Cambridge International Mathematics

24 Assumed Knowledge (Number)

1 Round correct to the number of significant figures shown in brackets.

a 42 : 3 [2] b 6 : 237 [3] c 0 : 0462 [2]

d 0 : 2461 [2] e 437 [2] f 2064 [2]

g 31 009 [3] h 10 : 27 [3] i 0 : 999 [1]

j 0 : 999 [2] k 264 003 [4] l 0 :037 642 [4]

m 3699 : 231 [4] n 0 :007 639 [2] o 29 999 [3]

p 69 : 7003 [2]

2 The crowd at a football match was officially

26 247people.

a Round the crowd size to:

i 1 significant figure

ii 2 significant figures.

b Which of these figures might be used by

the media to indicate crowd size?

3 The newspaper stated that 2500 people attended a protest march in Paris.

If this figure had been rounded to two significant figures, what was the largest number of people that

could have attended the protest?

4 During a rabbit plague there were132 709rabbits in South Australia. What figure would you expect to

see in a newspaper headline for an article on these rabbits?

ONE FIGURE APPROXIMATIONS

A fast way of estimating a calculation is to perform aone figure approximation. We round each number

in the calculation to one significant figure, then perform the calculation with these approximations.

² Leave single digit numbers as they are.

² Round all other numbers to one figure approximations.

² Perform the calculation.

For example, 3785 £ 7

¼ 4000 £ 7

¼28 000

Example 32 Self Tutor

Estimate the product: a 57 £ 8 b 537 £ 6

a Round off to the nearest 10.

57 £ 8

¼ 60 £ 8

¼ 480

b Round off to the nearest 100.

537 £ 6

¼ 500 £ 6

¼ 3000

Rules:

EXERCISE H.2

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Y:\HAESE\IGCSE01\IG01_AS\024IGCSE01_AS.CDR Wednesday, 10 September 2008 2:12:47 PM PETER
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