Answers to Coursebook exercises
3 Place value, ordering and rounding
F Exercise 3.1
1 a 323.5, 0.9 b 2.156, 4.777, 87.669
2 a 6 tenths b 3 tens c 1 thousandth
d 7 tenths e 9 units f 8 ten thousandths
3 a 9 units b 5 tenths c 8 hundredths
4 Yes. The number before the decimal place is the units (8) and there are also 953 thousandths in the number.
This shows that the number is bigger than 8 but smaller than 9.
5 4.05 kg
F Exercise 3.2
1 a 46 b 3.89 c 250 d 7 e 6500 f 38.9
g 70 h 0.422 i 6.2 j 0.43 k 0.42 l 0.0081
2 a 37 b 420 c 0.67 d 4.6
3 a ÷ b × c × d ÷ e ÷ f ×
4 a 10 b 10 c 1000 d 1000 e 100 f 100
g 1000 h 100 i 10
5 a 110 b 0.04 c 3.2 d 0.047 e 8.2, 0.82 f 0.3, 300
6 16 boxes
7 $0.35 or 35 cents
8 0.67
F Exercise 3.3
1 a 9.99 b 3.67 c 12.56 d 127.06 e 0.67 f 3.21
g 18.45 h 0.043 i 0.09
2 a 2.6, 3.31, 3.46, 3.49 b 0.52, 0.59, 0.71, 0.77 c 6.8, 6.82, 6.9, 6.97
d 5.199, 5.2, 5.212, 5.219 e 32.4, 32.42, 32.441, 32.448 f 9.03, 9.08, 9.7, 9.901, 9.99
3 a < b < c < d > e > f < g > h >
4 a 2.009, 2.15, 2.7 b 3.2, 3.342, 3.45 c 17.05, 17.1, 17.125, 17.42
5 Shelley-Ann Fraser. By putting the times in order: 10.49 s, 10.64 s, 10.65 s, 10.73 s,
10.74 s, 10.75 s
6 Any three numbers between 3.071 and 3.082
Copyright Cambridge University Press 2012 Cambridge Checkpoint Mathematics 7 1
Unit 3 Answers to Coursebook exercises
F Exercise 3.4
1 a 30 b 80 c 150 d 360 e 1480 f 3800
2 a 1000 b 3000 c 4000 d 8000 e 14 000 f 1000
3 Yes. Both ways round to 500.
4 a 0.6 b 8.3 c 2.5 d 9.2 e 12.9 f 0.1
5 Jason. His answer has one decimal number; Kylie’s does not.
F Exercise 3.5
1 a 7.7 b 8.3 c 17.2 d 3.4 e 7.4 f 7.8
2 a 12.2 b 18.5 c 26.1 d 3.5 e 10.5 f 14.4
3 No. She rounded 4.8 up to 5, which means she should subtract the extra 0.2 but she added the 0.2.
4 a 9.94 b 84.21 c 4.62 d 19.12
5 a $7.35 b $2.65
6 a 8.6 m b 1.4 m
7 a July b 86.53 kg
8 a 4 2 . 8 1 b 6 7 . 6 4
+ 2 6 . 3 5 – 2 9 . 5 8
6 9 . 1 6 3 8 . 0 6
F Exercise 3.6
1 a 0.8 b 0.9 c 2.5 d 4.2 e 1.8
2 a 13.5 b 28.8 c 29.4 d 6.3(0)
3 a 0.6 b 7 c 0.7 d 2 e 36.8 f 6.1, 18.3
4 Yes. 4 and 4.0 both have the same value.
F Exercise 3.7
1 a 2.1 b 2.3 c 0.7 d 2.8 e 1.3
2 a 4.13 b 2.31 c 1.21 d 3.11 e 9.01
3 $3.65
4 $1.16
5 a 3 . 1 9 b 2 . 6 5 c 5 . 8 9
2 6 . 3 1
8 3 7 . 19 5
1
6 3 5 . 53 4
5
2 Cambridge Checkpoint Mathematics 7 Copyright Cambridge University Press 2012
Answers to Coursebook exercises Unit 3
F Exercise 3.8
1 a 120 b 40 c 3500 d 3 e 1000
f 240 or 200 g 6000 h 35
2 a 116 b 43 c 3528 d 3.5 e 1049
f 228 g 6647 h 32
3 a i 25 ii 17.1 iii OK b i 13 ii 13.8 iii good
c i 2 ii 1.9 iii good d i 24 ii 20.3 iii good
4 a 160.4 b 27.57 c 96.6 d 15.43
5 a 16.6 + 24.8 = 41.4 km (check: e.g. 20 + 20 = 40)
b 70 − 41.4 = 28.6 km (check: e.g. 70 − 40 = 30)
6 a $28 × 6.5 = $182 (check: e.g. 30 × 7 = 210)
b $343 ÷ $28 = 12.25 hours (check: e.g. 300 ÷ 30 = 10)
7 36 × 75 = 5.4 She will need to buy 6 packs. (check: e.g. 40 × 80 = 6.4 )
500 500
End of unit review
1 0.66, 123.01, 2.39
2 a 3 tens b 7 hundredths c 2 thousandths d 0 tenths
3 a i 490 ii 0.23 iii 34 iv 8.76
b i 490 ÷ 10 = 49 ii 0.23 × 10 = 2.3 iii 34 ÷ 1000 = 0.034 iv 8.76 × 100 = 876
4 a 2.5 × 100 = 250 b 3.2 ÷ 1000 = 0.0032 c 17 × 10 = 1.7
5 4.2, 5.3, 5.49, 5.498
6 a 4750 b 4800 c 5000
7 a 76 b 76.2
8 a He rounded the hundredths first and then rounded to the nearest whole number. He should have just used
the tenths.
b 39
9 a 22.75 b 41.21 c 22.25 d 192.16
10 26.4 km
11 a 0.4 b 3.6 c 30.4 d 25.05
12 $4.63
13 a i 310 ii 316 iii good b i 6000 ii 6118 iii OK
14 4900 m
Copyright Cambridge University Press 2012 Cambridge Checkpoint Mathematics 7 3
