SmarterEd

Aussie Maths & Science Teachers: Save your time with SmarterEd

  • Login
  • Get Help
  • About

Functions, 2ADV EQ-Bank 9

The quantity \(y\) varies inversely with the square of \(x\).

When  \(x = 4, \ y = 10\).

Find the value of \(y\) when \(x = 8\).   (2 marks)

--- 6 WORK AREA LINES (style=lined) ---

Show Answers Only

\(y=\dfrac{5}{2}\)

Show Worked Solution

\(y \propto \dfrac{1}{x^2}\ \ \Rightarrow\ \ y= \dfrac{k}{x^2}\)

\(\text{When}\ \ x=4, \ y=10:\)

\(10= \dfrac{k}{4^2}\ \ \Rightarrow\ \ k=160\)
 

\(\text{Find}\ y\ \text{when}\ x=8:\)

\(y=\dfrac{160}{8^2}=\dfrac{5}{2}\)

Filed Under: Direct and Inverse Variation (Adv-2027), Further Functions and Relations (Y11) Tagged With: Band 4, smc-6383-30-prop 1/(kx^n), smc-987-60-Proportional

Functions, 2ADV F1 2022 HSC 12

A student believes that the time it takes for an ice cube to melt (`M` minutes) varies inversely with the room temperature `(T^@ text{C})`. The student observes that at a room temperature of `15^@text{C}` it takes 12 minutes for an ice cube to melt.

  1. Find the equation relating `M` and `T`.    (2 marks)

    --- 2 WORK AREA LINES (style=lined) ---

  2. By first completing this table of values, graph the relationship between temperature and time from `T=5^@C` to `T=30^@ text{C}`.   (2 marks)
     

\begin{array} {|c|c|c|c|}
\hline  \ \ T\ \  & \ \ 5\ \  & \ 15\  & \ 30\  \\
\hline M &  &  &  \\
\hline \end{array}

 
                   

--- 0 WORK AREA LINES (style=lined) ---

Show Answers Only

a.    `M=180/T`

 b.    

\begin{array} {|c|c|c|c|}
\hline  \ \ T\ \  & \ \ 5\ \  & \ 15\  & \ 30\  \\
\hline M & 36 & 12 & 6 \\
\hline \end{array}       

 

Show Worked Solution
a.    `M` `prop 1/T`
  `M` `=k/T`
  `12` `=k/15`
  `k` `=15 xx 12`
    `=180`

 
`:.M=180/T`
 


♦ Mean mark (a) 49%.

b.   

\begin{array} {|c|c|c|c|}
\hline  \ \ T\ \  & \ \ 5\ \  & \ 15\  & \ 30\  \\
\hline M & 36 & 12 & 6 \\
\hline \end{array}

Filed Under: Direct and Inverse Variation (Adv-2027), Further Functions and Relations (Y11), Variation and Rates of Change Tagged With: 2adv-std2-common, Band 4, Band 5, common-content, num-title-ct-patha, num-title-qs-hsc, smc-4239-30-a prop 1/b, smc-6383-30-prop 1/(kx^n), smc-987-30-Reflections and Other Graphs, smc-987-60-Proportional

Functions, 2ADV F1 EQ-Bank 7

The current of an electrical circuit, measured in amps `(A)`, varies inversely with its resistance, measured in ohms `(R)`.

When the resistance of a circuit is 28 ohms, the current is 3 amps.

What is the current when the resistance is 8 ohms?   (2 marks)

--- 6 WORK AREA LINES (style=lined) ---

Show Answers Only

`10.5`

Show Worked Solution

`A \prop 1/R\ \ =>\ \ A=k/R`

`text(When)\ \ A=3, \ R=28:`

`3` `=k/28`  
`k` `=84`  

 
`text(Find)\ A\ \text{when}\ R=8:`

`A=84/8=10.5`

Filed Under: Direct and Inverse Variation (Adv-2027), Further Functions and Relations (Y11) Tagged With: Band 4, smc-6383-30-prop 1/(kx^n), smc-987-60-Proportional

Copyright © 2014–2025 SmarterEd.com.au · Log in