Sometimes it is a good idea to estimate the value of a calculation rather than work it out exactly. In this situation, round the numbers in the question before performing the calculation. Usually, numbers are rounded to one significant figure. The 'approximately equal to' sign, ≈, is used to show that values have been rounded.

Estimate the value of .

Rounding to 1 significant figure gives:

Therefore:

Estimate:

Rounding to 1 significant figure gives:

Therefore:

- Question
Estimate the value of .

Rounding to 1 significant figure gives:

Therefore: .

- Question
Estimate .

Rounding to 1 significant figure gives:

Therefore: .