Round numbers to the nearest whole number, ten, hundred, etc. or to a given number of significant figures (sf) or decimal places (dp).

Round answers to an appropriate level of accuracy.

Esimate or check, without a calculator, the result of a calculaion by using suitable approximations.

e.g. Estimate, to one significant figure, the cost of 2.8 kg of potatoes at 68p per kg.

Estimate or check, without a calculator, the result of more complex calculations including roots.

Use the symbol ≈ appropriately.

e.g. \(\sqrt{\dfrac{2.9}{0.051×0.62}} ≈ 10\)

Use inequality notation to write down an error interval for a number or measurement rounded or truncated to a given degree of accuracy.

e.g. If x = 2.1 rounded to 1 dp, then \(2.05 \leq x < 2.15\).

If x = 2.1 truncated to 1 dp, then \(2.1 \leq x < 2.2\).

Apply and interpret limits of accuracy.

Calculate the upper and lower bounds of a calculation using numbers rounded to a known degree of accuracy.

e.g. Calculate the area of a rectangle with length and width given to 2 sf.

Understand the difference between bounds of discrete and continuous quantities.

e.g. If you have 200 cars to the nearest hundred then the number of cars \(n\) satisfies:
\(150 \leq n < 250 \) and
\(150 \leq n \leq 249 \)