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Measurement, STD2 M1 2009 HSC 25b (Adapted)

The mass of a sample of hungry cat fleas is 0.675 kilograms. There are approximately `1.5 × 10^6` hungry cat fleas in the sample.

In standard form, what is the approximate mass in grams of one hungry cat flea?   (2 marks)

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`4.5 xx 10^-4\ text(grams)`

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`text(Convert 0.675 kilograms into grams:)`

`0.675\ text(kg) = 0.675 xx 1000 = 675\ text(g)`

`:.\ text(Mass of 1 flea)` `= text(mass of sample)/text(# fleas)`
  `= (675)/(1.5 xx 10^6)`
  `= 4.5 xx 10^-4\ text(grams)`

v1 Measurement, STD2 M1 2020 HSC 2 MC

What is 0.0004782 expressed in standard form with two significant figures?

  1. `4.8 xx 10^(-4)`
  2. `4.78 xx 10^(-4)`
  3. `4.8 xx 10^(-5)`
  4. `4.78 xx 10^(-5)`
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`A`

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♦ Mean mark 39%.
COMMENT: Students often round incorrectly when converting to standard form.
`0.0004782` `= 4.782 xx 10^(-4)`
  `= 4.8 xx 10^(-4)\ \ \ text{(to 2 sig fig)}`

`⇒ A`

v1 Measurement, STD2 M1 2015 HSC 1 MC

The distance from Earth to the Moon is approximately 384 400 km.

What is this distance in standard form correct to two significant figures?

  1. `3.84 × 10^5\ \text{km}`
  2. `3.8 × 10^5\ \text{km}`
  3. `3.9 × 10^5\ \text{km}`
  4. `3.84 × 10^6\ \text{km}`
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`C`

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`384\ 400`

`= 3.844 × 10^5`

`\text(Rounded to 2 significant figures)  →  3.9 × 10^5\ \text{km}`

 
`⇒ C`