Page 30 - Cambridge+Checkpoint+Mathematics+Coursebook+9

3.3 Rounding

) Exercise 3.3

1 Round each number to the given degree of accuracy.
a 4.76 (1 decimal place (d.p.)) b 8.792 (2 d.p.) c 0.4766 (3 d.p.)
d 0.965 52 (2 d.p.) e 3.599 761 (4 d.p.) f 18.349 87 (3 d.p.)

2 Round the number 25.496 723 815 to the stated number of decimal places (d.p.).
a 3 d.p. b 1 d.p. c 5 d.p. d 4 d.p. e 2 d.p. f 7 d.p.

3 Round each number to the stated number of significant figures (s.f.).
a 135 (1 s.f.) b 45 678 (2 s.f.) c 18.654 (3 s.f.)
d 0.0931 (1 s.f.) e 0.7872 (2 s.f.) f 1.409 48 (3 s.f.)
4 Which answer is correct, A, B, C or D?
a 2569 rounded to 1 s.f. A 2 B 3 C 2000 D 3000
b 47.6821 rounded to 3 s.f. A 47.6 B 47.682 C 47.7 D 48.0
c 0.0882 rounded to 2 s.f. A 0.08 B 0.088 C 0.09 D 0.1
d 3.089 62 rounded to 4 s.f. A 3.089 B 3.0896 C 3.09 D 3.090

5 Round the number 4509.0298 to the stated number of significant figures (s.f.).
a 3 s.f. b 1 s.f. c 5 s.f. d 4 s.f. e 2 s.f. f 7 s.f.
6 At a football match there were 63 475 Barcelona supporters and 32 486
Arsenal supporters.
How many supporters were there altogether?

Give your answer correct to two significant figures.
7 Ahmad has a bag of peanuts that weighs 150 g.
There are 335 peanuts in the bag.
Work out the average (mean) mass of a peanut.

Give your answer correct to one significant figure.
8 The speed of light is approximately 670 616 629 miles per hour. The symbol 5 means ‘is
Use the conversion 1 mile 5 1.6 km to work out the speed of light approximately equal to’.
in metres per second.
cant fi gures.

Give your answer correct to three signifi
Give your answer correct to three significant figures.
9 This is part of Jake’s homework. 0 238 576
×
.
He works out an estimate by Question a Work out an estimate of 39 76 .
.
rounding each number to one b Work out the accurate value.

significant figure. c Compare your estimate with the
o
r ea
e
ps f
c
f
the
h o
Follow these steps for each of the accurate value.
w these st
ol
F
lo
Follow these steps for each of the
Answer
calculations below. Answer a § § §
Answer
ê ¸ (VWLPDWH WH
i Use Jake’s method to work ê ¸ (VWLPD
out an estimate of the answer.
out an estimate of the answer. b ê
ii Use a calculator to work out ¸ V I
$FFXUDWH V I
the accurate answer. Give this c My estimate is close to my accurate
the accurate answer. Give this
answer correct to three DQVZHU VR P\ DFFXUDWH DQVZHU LV

significant figures. probably correct.
iii Compare your estimate
with the accurate answer. Decide if your accurate answer is correct.
×
.
.
.
.
a 03941 196 b 4732 + 9176 c 2764 × 84695 d 58432 × 008
.
.
.
.
4796 195166 9687 − 419 02 × 348
.
3 Place value, ordering and rounding 29