Fully worked, step-by-step solutions to GCSE Estimation and checking questions. See exactly how to solve problems on rounding to 1 s.f., decimals, estimating, multiplication.
Find the first significant figure
The first significant figure of 68 is the 6, in the tens column.
Look at the next digit
The next digit is 8. Since 8 ≥ 5, round the tens digit up.
Write the rounded number
6 tens becomes 7 tens and the units digit becomes 0, so 68 ≈ 70.
Find the first significant figure
The first significant figure of 34 is the 3, in the tens column.
Look at the next digit
The next digit is 4. Since , round down (leave the tens digit).
Write the rounded number
The tens digit stays 3 and the units become 0, so 34 ≈ 30.
Find the first significant figure
The first significant figure is 4, in the hundreds column.
Look at the next digit
The next digit is 5. Since 5 ≥ 5, round the hundreds digit up.
Write the rounded number
4 hundreds becomes 5 hundreds and the rest become 0, so 452 ≈ 500.
Find the first significant figure
The first significant figure is 7, in the units column.
Look at the next digit
The next digit is 3. Since , round down.
Write the rounded number
The units digit stays 7, so 7.3 ≈ 7.
Find the first significant figure
Leading zeros are not significant; the first significant figure is 5, in the hundredths column.
Look at the next digit
The next digit is 8. Since 8 ≥ 5, round the hundredths digit up.
Write the rounded number
5 hundredths becomes 6 hundredths, so 0.058 ≈ 0.06.
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