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Algebra, STD2 EQ-Bank 25

A fitness app calculates daily calorie requirements using the formula below.

Daily calories = Basal metabolic rate + Calorie burn rate per hour \( \times \) Hours of activity

The spreadsheet below has been used to calculate Jamal's daily calorie requirements when he has had 6 hours of activity.
  

  1. Write down the formula used in cell B9, using appropriate grid references.   (1 mark)

  2. Jamal increases his hours of activity to 8 hours per day, while his basal metabolic rate and calorie burn rate remain the same.

    What will be Jamal's new daily calorie requirement?   (1 mark)

Show Answers Only

a.    \(=\text{B4}+ \text{B5} \ ^* \ \text{B6}\)

b.    \(2770\ \text{calories}\)

Show Worked Solution

a.   \(=\text{B4}+ \text{B5} \ ^* \ \text{B6}\)

b.    \(\text{Daily calories}\) \(=1650+140\times 8\)
    \(=2770\)

\(\therefore\ \text{Jamal’s new daily calorie requirement is}\ 2770.\)

Algebra, STD2 EQ-Bank 24

QuickPrint Copy Centre charges for printing services using the formula below.

Total cost = Setup fee + Cost per page \( \times \) Number of pages

A spreadsheet used to calculate the total cost is shown.

  1. Write down the formula used in cell E3, using appropriate grid references.   (1 mark)

  2. QuickPrint increases their cost per page to \$0.42, but keeps the setup fee unchanged. Aisha needs to print 120 pages.

    How much more will Aisha pay compared to the original pricing shown in the spreadsheet?   (2 marks)

Show Answers Only

a.    \(=\text{B3}+ \text{B4} \ ^* \ \text{B5}\)

b.    \($14.40\)

Show Worked Solution

a.   \(=\text{B3}+ \text{B4} \ ^* \ \text{B5}\)
 

b.   \(\text{Original cost from spreadsheet}:\ $44.50\)

\(\text{At increased rate}:\)

\(\text{Total cost}\ =8.50+0.42\times 120=$58.90\)

\(\text{Additional amount}\ =58.90-44.50=$14.40\)

Algebra, STD2 EQ-Bank 23

Green Thumb Landscaping charges for their lawn mowing service based on the size of the lawn.

They use the formula below to calculate the cost of each service.

Total cost = Call-out fee + Cost per square metre \( \times \) Area of lawn

The spreadsheet they provide to their clients is included below.

  1. Write down the formula that has been used in cell E4, using appropriate grid references.   (1 mark)

  2. Miguel has a lawn with a different area. The call-out fee and cost per square metre remain the same. When Miguel's lawn area is entered into the spreadsheet, the total cost shown in cell E4 becomes \$153.00.

    What is the area of Miguel's lawn?   (2 marks)

Show Answers Only

a.    \(=\text{B4}+ \text{B5} \ ^* \ \text{B6}\)

b.    \(\text{60 m}^2\)

Show Worked Solution

a.    \(=\text{B4}+ \text{B5} \ ^* \ \text{B6}\)
 

b.     \(153\) \(=45+1.8A\)
  \(108\) \(=1.8A\)
  \(A\) \(=\dfrac{108}{1.8}=60\)

 
\(\therefore\ \text{The area of Miguel’s lawn is 60m}^2.\)

Algebra, STD2 EQ-Bank 27

Dial-A-Lift Luxury Transport offers ride services in the local area of Maitland.

They currently use the formula below to calculate the cost of each fare.

   Total fare \(=\) Booking fee \(+\) Cost per kilometre \(\times\) Number of kilometres travelled

A spreadsheet used to calculate the total fare is shown.
 

  1. By using appropriate grid references, write down a formula that could have been used in cell E4.   (2 marks)

  2. A trip with a different number of kilometres travelled is entered, but the booking fee and cost per kilometre remain unchanged. As a result, the value in cell E4 changes to $47.50.
  3. Calculate the value entered in cell B6.   (2 marks)

Show Answers Only

a.    \(=\text{B4}+ \text{B5} \ ^* \ \text{B6}\)

b.    \(\text{Cell B6 value = 13.}\)

Show Worked Solution

a.    \(=\text{B4}+ \text{B5} \ ^* \ \text{B6}\)
 

b.     \(47.5\) \(=15+2.5 n\)
  \(32.5\) \(=2.5n\)
  \(n\) \(=\dfrac{32.5}{2.5}=13\)

 
\(\text{Cell B6 value = 13.}\)

Algebra, STD2 EQ-Bank 25

The following formula can be used to calculate the recommended dosage of a medicine for a child.

   Recommended dosage \(=\) base dosage \(+\) adjustment factor \(\times\) weight of child,

where the recommended dosage and base dosage are in milligrams and the weight of the child is in kilograms.

A spreadsheet used to calculate the recommended dosage is shown.
 

  1. By using appropriate grid references, write down a formula that could have been used in cell E5.   (2 marks)

  2. The weight of a different child is entered, but the base dosage and adjustment factor remain unchanged. As a result, the value in cell E5 changes to 70.
  3. Calculate the value entered in cell B7.   (2 marks)

Show Answers Only

a.    \(=\text{B5}+ \text{B6} \ ^* \ \text{B7}\)

b.    \(\text{Cell B7 value = 25.}\)

Show Worked Solution

a.    \(=\text{B5}+ \text{B6} \ ^* \ \text{B7}\)
 

b.    \(\text{Let \(w\) = weight of the child}\)

\(70\) \(=50+0.8 w\)
\(20\) \(=0.8 w\)
\(w\) \(=\dfrac{20}{0.8}=25\)

 
\(\text{Cell B7 value = 25.}\)

Algebra, STD2 EQ-Bank 4 MC

The graph shows the tax payable against taxable incomes up to $60 000 in a proposed tax system.

How much of each dollar earned over \($30\,000\) is payable in tax?

  1.  10 cents
  2. 12 cents
  3. 20 cents
  4. 23 cents
Show Answers Only

\(C\)

Show Worked Solution

\(\text{The gradient of line represents the tax payable per dollar.}\)

\(\text{Tax payable per dollar}:\)

\(= \dfrac{\text{rise}}{\text{run}}= \dfrac{7000-1000}{60\ 000-30\ 000}\)

\(=\dfrac{1}{5}=0.20\)

\(\therefore\ \text{20 cents per dollar is payable in tax after }$30\, 000.\)

\(\Rightarrow C\)

Algebra, STD2 EQ-Bank 16

Jerico is the manager of a weekend market in which there are 220 stalls for rent. From past experience, Jerico knows that if he charges \(d\) dollars to rent a stall. then the number of stalls, \(s\), that will be rented is given by:

\(s=220-4d\)

  1. How many stalls will be rented if Jerico charges $7.50 per stall .   (1 mark)

  2. Complete the following table for the function  \(s=220-4d\).   (1 mark)

\begin{array} {|c|c|c|}
\hline
\rule{0pt}{2.5ex} \quad d\quad \rule[-1ex]{0pt}{0pt} & \rule{0pt}{2.5ex} \quad 10\quad\rule[-1ex]{0pt}{0pt} & \rule{0pt}{2.5ex} \quad 30\quad & \rule{0pt}{2.5ex} \quad 50\quad \\
\hline
\rule{0pt}{2.5ex} \quad s\quad \rule[-1ex]{0pt}{0pt} & \ & \ & \\
\hline
\end{array}

  1. Using an appropriate vertical scale and labelled axes, graph the function  \(s=220-4d\) on the grid below.   (2 marks)
  1. Does it make sense to use the formula  \(s=220-4d\)  to calculate the number of stalls rented if Jerico charges $60 per stall? Explain your answer.   (2 marks)

Show Answers Only
  

a.    \(190\ \text{stalls will be rented}\)

b.

\begin{array} {|c|c|c|}
\hline
\rule{0pt}{2.5ex} \quad d\quad \rule[-1ex]{0pt}{0pt} & \rule{0pt}{2.5ex} \quad 10\quad\rule[-1ex]{0pt}{0pt} & \rule{0pt}{2.5ex} \quad 30\quad & \rule{0pt}{2.5ex} \quad 50\quad \\
\hline
\rule{0pt}{2.5ex} \quad s\quad \rule[-1ex]{0pt}{0pt} & 180 \ & 100 \ & 20  \\
\hline
\end{array}

c.

d.    \(\text{When}\ d=60, s=220-4\times 60=-20\)

\(\therefore\ \text{It does not make sense to charge }$60\ \text{ per stall}\)

\(\text{as you cannot have a negative number of stalls.}\)

Show Worked Solution

a.    \(s=220-4d=220-4\times 7.50=190\)

\(\therefore 190\ \text{stalls will be rented}\)

b.

\begin{array} {|c|c|c|}
\hline
\rule{0pt}{2.5ex} \quad d\quad \rule[-1ex]{0pt}{0pt} & \rule{0pt}{2.5ex} \quad 10\quad\rule[-1ex]{0pt}{0pt} & \rule{0pt}{2.5ex} \quad 30\quad & \rule{0pt}{2.5ex} \quad 50\quad \\
\hline
\rule{0pt}{2.5ex} \quad s\quad \rule[-1ex]{0pt}{0pt} & 180 \ & 100 \ & 20  \\
\hline
\end{array}

c.

d.    \(\text{When}\ d=60, s=220-4\times 60=-20\)

\(\therefore\ \text{It does not make sense to charge }$60\ \text{ per stall}\)

\(\text{as you cannot have a negative number of stalls.}\)

Algebra, STD2 A4 2022 HSC 22

The formula  `C=100 n+b`  is used to calculate the cost of producing laptops, where `C` is the cost in dollars, `n` is the number of laptops produced and `b` is the fixed cost in dollars.

  1. Find the cost when 1943 laptops are produced and the fixed cost is $20 180.   (1 mark)

  2. Some laptops have some extra features added. The formula to calculate the production cost for these is
  3.      `C=100 n+a n+20\ 180`
  4. where `a` is the additional cost in dollars per laptop produced.
  5. Find the number of laptops produced if the additional cost is $26 per laptop and the total production cost is $97 040.   (2 marks)

Show Answers Only

a.    `$214\ 480`

b.    `610\ text{laptops}`

Show Worked Solution

a.   `text{Find}\ \ C\ \ text{given}\ \ n=1943 and b=20\ 180`

`C=100 xx 1943 + 20\ 180=$214\ 480`

b.   `text{Find}\ \ n\ \ text{given}\ \ C=97\ 040 and a=26`

`C` `=100 n+a n+20\ 180`  
`97\ 040` `=100n + 26n +20\ 180`  
`126n` `=76\ 860`  
`n` `=(76\ 860)/126=610 \ text{laptops}`  

Algebra, STD2 A2 2022 HSC 16

Tom is 25 years old, and likes to keep fit by exercising.

  1. Use this formula to find his maximum heart rate (bpm).   (1 mark)
  2.      Maximum heart rate = 220 – age in years

  3. Tom will get the most benefit from this exercise if his heart rate is between 50% and 85% of his maximum heart rate.
  4. Between what two heart rates should Tom be aiming for to get the most benefit from his exercise?   (2 marks)

Show Answers Only

a.   `text{195 bpm}`

b.   `98-166\ text{bpm}`

Show Worked Solution
a.    `text{Max heart rate}` `=220-25`
    `=195\ text{bpm}`

 

b.   `text{50% max heart rate}\ = 0.5 xx 195 = 97.5\ text{bpm}`

`text{85% max heart rate}\ = 0.85 xx 195 = 165.75\ text{bpm}`

`:.\ text{Tom should aim for between 98 and 166 bpm in exercise.}`

Algebra, STD1 A3 2021 HSC 25

The diagram shows a container which consists of a small cylinder on top of a larger
cylinder.
 


 

The container is filled with water at a constant rate to the top of the smaller cylinder. It takes 5 minutes to fill the larger cylinder.

Draw a possible graph of the water level in the container against time.   (2 marks)
 

Show Answers Only

Show Worked Solution
♦ Mean mark 38%.

Algebra, STD2 A2 2021 HSC 18

The fuel consumption for a car is 6.7 litres/100 km. On a road trip, the car travels a distance of 1560 km and the fuel cost is $1.45 per litre.

What is the total fuel cost for the trip?   (2 marks)

Show Answers Only

`$151.55`

Show Worked Solution

`text(Total fuel used)=6.7 xx 1560/100=104.52\ text(L)`

`text(Total fuel cost)=104.52 xx 1.45=$151.55`

Algebra, STD2 A2 2020 HSC 10 MC

A plumber charges a call-out fee of $90 as well as $2 per minute while working.

Suppose the plumber works for `t` hours.

Which equation expresses the amount the plumber charges ($`C`) as a function of time (`t` hours)?

  1. `C = 2 + 90t`
  2. `C = 90 + 2t`
  3. `C = 120 + 90t`
  4. `C = 90 + 120t`
Show Answers Only

`D`

Show Worked Solution

♦ Mean mark 42%.

`text(Hourly rate)\ = 60 xx 2=$120`

`:. C = 90 + 120t`

`=>D`

Algebra, STD2 A2 EQ-Bank 3 MC

A car travels 350 km on 40 L of petrol.

What is its fuel consumption?

  1. 7.8 L/100 km
  2. 8.4 L/100 km
  3. 8.8 L/100 km
  4. 11.4 L/100 km
Show Answers Only

`D`

Show Worked Solution

`text(40 litres are used to travel  3.5 × 100 km.)`

`text{Fuel consumption (L/100 km)}`

`= 40/3.5 = 11.428 = 11.4\ text(L/100 km)`

`=> D`

Algebra, STD2 A2 EQ-Bank 29

The average height, `C`, in centimetres, of a girl between the ages of 6 years and 11 years can be represented by a line with equation

`C = 6A + 79`

where `A` is the age in years. For this line, the gradient is 6.

  1. What does this indicate about the heights of girls aged 6 to 11?   (1 mark)

  2. Give ONE reason why this equation is not suitable for predicting heights of girls older than 12.   (1 mark)

Show Answers Only

a.    `text(It indicates that 6-11 year old girls, on average, grow 6 cm per year.)`

b.    `text(Girls eventually stop growing, and the equation doesn’t factor this in.)`

Show Worked Solution

a.  `text(It indicates that 6-11 year old girls, on average, grow 6 cm per year.)`

b. `text(Girls eventually stop growing, and the equation doesn’t factor this in.)`

Algebra, STD2 A2 2018 HSC 5 MC

The driving distance from Alex's home to his work is 20 km. He drives to and from work five times each week. His car uses fuel at the rate of 8 L/100 km.

How much fuel does he use driving to and from work each week?

  1. 16 L
  2. 20 L
  3. 25 L
  4. 40 L
Show Answers Only

`A`

Show Worked Solution

`text(Total distance travelled each week)`

`= 5 xx 2 xx 20= 200\ text(km)` 

`:.\ text(Total fuel used)`

`= 200/100 xx 8\ text(L)= 16\ text(L)`

`=>A`

Algebra, STD2 A2 2017 HSC 14 MC

Kate is comparing two different models of car. Car A uses fuel at the rate of 9 L/100 km. Car B uses 3.5 L/100 km.

Suppose Kate plans on driving 8000 km in the next year.

How much less fuel will she use driving car B instead of car A?

  1. 280 L
  2. 440 L
  3. 720 L
  4. 1000 L
Show Answers Only

`B`

Show Worked Solution

`text(Fuel car)\ A= 8000/100 xx 9= 720\ text(L)`

`text(Fuel car)\ B= 8000/100 xx 3.5= 280\ text(L)`

`:.\ text(Fuel saved car)\ B= 720-280= 440\ text(L)`

`=>B`

Algebra, STD2 A2 2017 HSC 3 MC

The graph shows the relationship between infant mortality rate (deaths per 1000 live births) and life expectancy at birth (in years) for different countries.
 

What is the life expectancy at birth in a country which has an infant mortality rate of 60?

  1. 68 years
  2. 69 years
  3. 86 years
  4. 88 years
Show Answers Only

\(A\)

Show Worked Solution

\(\text{When infant mortality rate is 60, life expectancy}\)

\(\text{at birth is 68 years (see below).}\)
 

\(\Rightarrow A\)

Algebra, STD2 A2 2016 HSC 29e

The graph shows the life expectancy of people born between 1900 and 2000.
 


  1. According to the graph, what is the life expectancy of a person born in 1932?   (1 mark)

  2. With reference to the value of the gradient, explain the meaning of the gradient in this context.   (2 marks)

Show Answers Only

a.    `text(68 years)`

b.    `text(After 1900, life expectancy increases 0.25 years for each later year someone is born.)`

Show Worked Solution

a.    \(\text{68 years}\)

b.    \(\text{Using (1900,60), (1980,80):}\)

\(\text{Gradient}\) \(= \dfrac{y_2-y_1}{x_2-x_1}\)
  \(= \dfrac{80-60}{1980-1900}\)
  \(= 0.25\)

 
\(\text{After 1900, life expectancy increases by 0.25 years for}\)

\(\text{each year later that someone is born.}\)

♦♦ Mean mark (ii) 33%.

Algebra, STD2 A2 2016 HSC 26c

Peta’s car uses fuel at the rate of 5.9 L /100 km for country driving and 7.3 L /100 km for city driving. On a trip, she drives 170 km in the country and 25 km in the city.

Calculate the amount of fuel she used on this trip.   (2 marks)

Show Answers Only

`11.855\ text(L)`

Show Worked Solution

`text(Fuel used in country)= 170 xx 5.9/100= 10.03\ text(L)`

`text(Fuel used in city)= 25 xx 7.3/100= 1.825\ text(L)`

`:.\ text(Total fuel used)= 10.03 + 1.825= 11.855\ text(L)`

Algebra, STD2 A2 2007 HSC 27b

A clubhouse uses four long-life light globes for five hours every night of the year. The purchase price of each light globe is $6.00 and they each cost  `$d`  per hour to run.

  1. Write an equation for the total cost (`$c`) of purchasing and running these four light globes for one year in terms of  `d`.   (2 marks)

  2. Find the value of  `d`  (correct to three decimal places) if the total cost of running these four light globes for one year is $250.   (1 mark)

  3. If the use of the light globes increases to ten hours per night every night of the year, does the total cost double? Justify your answer with appropriate calculations.   (1 mark)

  4. The manufacturer’s specifications state that the expected life of the light globes is normally distributed with a standard deviation of 170 hours.

     

    What is the mean life, in hours, of these light globes if 97.5% will last up to 5000 hours?   (1 mark)

Show Answers Only
  1. `$c = 24 + 7300d`
  2. `0.031\ $ text(/hr)\ text{(3 d.p.)}`
  3. `text(Proof)\ \ text{(See Worked Solutions)}`
  4. `text(4660 hours.)`
Show Worked Solution

a.   `text(Purchase price) = 4 xx 6 = $24`

`text(Running cost)` `= text(# Hours) xx text(Cost per hour)`
  `= 4 xx 5 xx 365 xx d= 7300d`

`:.\ $c = 24 + 7300d`

b.   `text(Given)\ \ $c = $250`

`250` `= 24 + 7300d`
`7300d` `= 226`
`d` `= 226/7300= 0.03095…`
  `= 0.031\ $ text(/hr)\ text{(3 d.p.)}`

 

c.    `text(If)\ d\ text(doubles to 0.062)\ \ $text(/hr)`

`$c= 24 + 7300 xx 0.062= $476.60`

`text(S) text(ince $476.60 is less than)\ 2 xx $250\ ($500),`

`text(the total cost increases to less than double)`

`text(the original cost.)`

d.  `sigma = 170`

`z\ text(-score of 5000 hours) = 2`

`z` `= (x – mu)/sigma`
`2` `= (5000 – mu)/170`
`340` `= 5000 – mu`
`mu` `= 4660`

 

`:.\ text(The mean life of these globes is 4660 hours.)`

Algebra, STD2 A2 2014 HSC 27b

Xuso is comparing the costs of two different ways of travelling to university.

Xuso’s motorcycle uses one litre of fuel for every 17 km travelled. The cost of fuel is $1.67/L and the distance from her home to the university car park is 34 km. The cost of travelling by bus is  $36.40 for 10 single trips.

Which way of travelling is cheaper and by how much? Support your answer with calculations.   (2 marks)

Show Answers Only

`text(Motorcycle is $0.30 cheaper per 1-way trip)`

Show Worked Solution

`text(Compare cost of a 1-way trip)`

`text(Motorcycle)`

`text(Fuel used) = 34/17 = 2\ text(L)`

`text(C)text(ost) = 2 xx $1.67 = $3.34`

`text(Bus)`

`text(C)text(ost) = 36.40/10 = $3.64`

`text(Difference) = $3.64\-3.34\ = $0.30`

 

`:.\ text(Motorcycle is $0.30 cheaper per 1-way trip.)`

Algebra, STD2 A2 2014 HSC 22 MC

Heather’s car uses fuel at the rate of 6.6 L per 100 km for long-distance driving and  8.9 L per 100 km for short-distance driving.

She used the car to make a journey of 560 km, which included 65 km of short-distance driving.  

Approximately how much fuel did Heather’s car use on the journey?

  1. 37 L
  2. 38 L
  3. 48 L
  4. 50 L
Show Answers Only

`B`

Show Worked Solution

`text(Fuel used in short distance)`

`= 65/100 xx 8.9\ text(L) = 5.785\ text(L)`

`text(Fuel used in long distance)`

`= 495/100 xx 6.6\ text(L) = 32.67\ text(L)`

`:.\ text(Total Fuel)= 38.455\ text(L)`  

`=>  B`

Algebra, STD2 A2 2010 HSC 27c

The graph shows tax payable against taxable income, in thousands of dollars.

2010 27c

  1. Use the graph to find the tax payable on a taxable income of $21 000.   (1 mark)

  2. Use suitable points from the graph to show that the gradient of the section of the graph marked  `A`  is  `1/3`.   (1 mark)

  3. How much of each dollar earned between  $21 000  and  $39 000  is payable in tax?   (1 mark)

  4. Write an equation that could be used to calculate the tax payable, `T`, in terms of the taxable income, `I`, for taxable incomes between  $21 000  and  $39 000.   (2 marks)

Show Answers Only
  1. `$3000\ \ \ text{(from graph)}`
  2. `1/3`
  3. `33 1/3\ text(cents per dollar earned)`
  4. `text(Tax payable on)\ I = 1/3 I\-4000`
Show Worked Solution
a.

 `text(Income on)\ $21\ 000=$3000\ \ \ text{(from graph)}`

 

b.   `text(Using the points)\ (21,3)\ text(and)\ (39,9)`

♦♦ Mean mark 25%
`text(Gradient at)\ A` `= (y_2\-y_1)/(x_2\ -x_1)`
  `= (9000-3000)/(39\ 000-21\ 000)`
  `= 6000/(18\ 000)`
  `= 1/3\ \ \ \ \ text(… as required)`

 

c.    `text(The gradient represents the tax applicable to each dollar)`

♦♦♦ Mean mark 12%!
MARKER’S COMMENT: Interpreting gradients is an examiner favourite, so make sure you are confident in this area.
`text(Tax)` ` = 1/3\ text(of each dollar earned)`
  ` = 33 1/3\ text(cents per dollar earned)`

 

d.    `text( Tax payable up to $21 000 = $3000)`

`text(Tax payable on income between $21 000 and $39 000)`

♦♦♦ Mean mark 15%.
STRATEGY: The earlier parts of this question direct students to the most efficient way to solve this question. Make sure earlier parts of a question are front and centre of your mind when devising strategy.

` = 1/3 (I\-21\ 000)`

`:.\ text(Tax payable on)\ \ I` `= 3000 + 1/3 (I\-21\ 000)`
  `= 3000 + 1/3 I\-7000`
  `= 1/3 I\-4000`

Algebra, STD2 A2 2009 HSC 24d

A factory makes boots and sandals. In any week

• the total number of pairs of boots and sandals that are made is 200
• the maximum number of pairs of boots made is 120
• the maximum number of pairs of sandals made is 150.

The factory manager has drawn a graph to show the numbers of pairs of boots (`x`) and sandals (`y`) that can be made.
 

 

  1. Find the equation of the line `AD`.   (1 mark)

  2. Explain why this line is only relevant between `B` and `C` for this factory.   (1 mark)

  3. The profit per week, `$P`, can be found by using the equation  `P = 24x + 15y`.

     

    Compare the profits at `B` and `C`.   (2 marks)

Show Answers Only
  1. `x + y = 200`
  2. `text(S)text(ince the max amount of boots = 120)`

     

    `=> x\ text(cannot)\ >120`

     

    `text(S)text(ince the max amount of sandals = 150`

     

    `=> y\ text(cannot)\ >150`

     

    `:.\ text(The line)\ AD\ text(is only possible between)\ B\ text(and)\ C.`

  3. `text(The profits at)\ C\ text(are $630 more than at)\ B.`
Show Worked Solution

a.   `text{We are told the number of boots}\ (x),` 

♦♦♦ Mean mark part (i) 14%. 
Using `y=mx+b` is a less efficient but equally valid method, using  `m=–1`  and  `b=200` (`y`-intercept).

`text{and shoes}\  (y),\ text(made in any week = 200)`

`=>text(Equation of)\ AD\ text(is)\ \ x + y = 200`

 

b.   `text(S)text(ince the max amount of boots = 120)`

♦ Mean mark 49%

`=> x\ text(cannot)\ >120`

`text(S)text(ince the max amount of sandals = 150`

`=> y\ text(cannot)\ >150`

`:.\ text(The line)\ AD\ text(is only possible between)\ B\ text(and)\ C.`

 

c.   `text(At)\ B,\ \ x = 50,\ y = 150`

♦ Mean mark 40%.
`=>$P  (text(at)\ B)` `= 24 xx 50 + 15 xx 150`
  `= 1200 + 2250`
  ` = $3450`

`text(At)\ C,\ \  x = 120 text(,)\ y = 80`

`=> $P  (text(at)\ C)` `= 24 xx 120 + 15 xx 80`
  `= 2880 + 1200`
  `= $4080`

 

`:.\ text(The profits at)\ C\ text(are $630 more than at)\ B.`

Algebra, STD2 A2 2009 HSC 13 MC

The volume of water in a tank changes over six months, as shown in the graph.
 

 2UG-2010-13MC

 
Consider the overall decrease in the volume of water.

What is the average percentage decrease in the volume of water per month over this time, to the nearest percent?

  1. 6%
  2. 11%
  3. 32%
  4. 64%
Show Answers Only

`B`

Show Worked Solution
♦ Mean mark 48%
COMMENT: Remember that % decrease requires the decrease in volume to be divided by the original volume (50,000L).

`text(Initial Volume)= 50\ 000\ text(L)`

`text(Final volume)= 18\ 000\ text(L)`

`text(Decrease 6 mths)= 50\ 000-18\ 000= 32\ 000\ text(L)`

`text(Loss per month)=5333.33…\ text(L/month)` 

`text(% loss per month)= (5333.33…)/( 50\ 000)=10.666… %` 

 
`=>  B`