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Rounding and estimation

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# 1.4.1 Try some yourself

## Activity 5

Round a measurement of 1.059 metres:

• (a) to the nearest whole number of metres;

• (b) to two decimal places;

• (a) 1.059 m rounded to the nearest whole number of metres is 1 m.

• (b) 1.059 m rounded to two decimal places is 1.06 m.

## Activity 6

Round each of the numbers below to:

• (a) to 1 d.p.

• (b) to 2 d.p.

• (c) to 3 d.p.

0.472 65,  13.959 943,  56.098 27

• (a) 0.5,  14.0,  56.1

• (b) 0.47,  13.96,  56.10

• (c) 0.473,  13.960,  56.098

## Activity 7

The table below contains some errors. Identify them and write down the correct rounding.

Rounded to
Number1 d.p.2 d.p.3 d.p.
3.141 592 63.103.143.150
22/73.13.043.142
0.019 9990.00.190.200

The corrected entries are in bold.

Rounded to
Number1 d.p.2 d.p.3 d.p.
3.141 592 63.13.143.142
22/73.13.143.143
0.019 9990.00.020.020

## Activity 8

Imagine you are alone on an island and that your only source of drinking water is a wrecked ship's full water tank. It measures 4 metres long by 3.45 metres wide and is 2.84 metres high. Use reasonable rounded values to make an estimate (without using your calculator) of how long you can survive until it rains, assuming that you need 2 litres per day and that the water remains perfectly fresh. You may need the conversion 1 cubic metre contains 1000 litres. (Note that volume = length × width × height.)