Significant figures are the digits in a number that contribute to the accuracy of the number.

A quick estimate for a calculation is obtained from using approximate values, often rounded to 1 significant figure.

Checking by estimating

Maths

In this unit, pupils have learnt how to round to a given number of decimal places or significant figures and explored the effect of using rounded numbers for calculations. In the future unit, pupils will investigate the bounds and perform calculations to determine a best/worst case scenario.

The prior unit on place value allowed pupils to develop the skills needed to estimate and round values. By understanding the value of each digit, pupils can determine what other values are close to the original value. This unit continues the exploration of the infinite nature of sets of numbers.

Estimation and rounding

Match the following numbers to the correct rounded value.

Which of the following is a sensible measurement for the lengths of an average house?

A bookshop wants to buy the new sci-fi books to sell in their store. The bookshop has £789 and each book costs £18.99. Select the correct estimate for the number of books the bookshop can buy.

Select the approximate answer to $$\frac{8}{15}\times\ 9$$.

A bicycle costs £18.99 for 1 week's hire. Which of the following shows the estimate to hire 6 bicycles for 4 weeks? 

Jun buys paper £3.25, USB £$$\square$$, stamps £4.95, crisps £0.85, staples £2.30 and plug £1.99. He pays with a £20 note and receives about £2 back in change. Estimate the cost of the USB.

Significant figures are the digits in a number that contribute to the accuracy of the number.  The first significant figure is the first __________ digit.

Which of the following are good estimate calculations for 989 × 213.4?

Which of the following are good, quick estimate calculations for 432.4 ÷ 1.85?

Which of the following are correct estimates for $${17.9}\over {0.532}$$?

$${3.4\times3.92}\over {0.511}$$ $$ = 26.082$$

Which of the following is the correct estimate for $${3.4\times3.92}\over {0.511}$$?

Horses and ponies are measured using ‘hands’ as a unit, where the width of the hand is used. This pony has a height of 9 hands. Estimate the height of the pony.

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