Page 87 - Math Smart - 7

4.2.3 Multiplying decimals In this chapter
Pupils should be able to:
• multiply decimals with
Example 4
one and/or two places
by single-digit numbers
O Kifn uses 13.7 i of water to wash her car. How many litres of water will she
need to wash 8 identical cars?

We need to find the product of 13.7 x 8. ^ RECALL
+2 +5
There is one digit after the decimal point.
13.7^ Find the product.
X 8
To place the decimal point in the 15.8
109. 6-^-
correct position in the answer, count X 4
KJ
one digit from the right in the answer.
She will need 109.6 litres of water to wash 8 identical cars.

O Mia needs 2.12 metres of material to make one curtain. How many metres of
material will Mia need to make 3 identical curtains. We need to multiply.
2.12 X 3 = ?
There are two digits after the decimal point.
2.12'
X 3
To place the decimal point in the correct
6.36 '
position in the answer, count two digits
from the right in the answer.

Mia will need 6.36 m of material to make 3 identical curtains.

Check My

Understanding

Multiply.
O a) 1 X 2.3 b) 3 X 4.2 c) 0.5 X 2 d) 0.1 X 0 e) 2 X 7.8

f) 4 X 1.9 g) 5.3 X 3 h) 0.9 X 9 I) 4.4 X 4 j) 9 X 8.9
a)
0 1 X 2.38 b) 2 X 4.32 c) 0.51 X 4 d) 0.07 X 3 e) 2 X 7.88
f) 6X1.29 g) 5.03 X 6 h) 0.88 X 6 i) 4.06 X 4 j) 9 X 17.9
a)
0 0.8 X 8 b) 5 X 4.02 c) 6.5 X 6 d) 1.2 X 9 e) 2 X 0.32
f) 9.09 X 2 g) 4.5 X 7 h) 18.23 X 5 i) 23.07 X 3 j) 52.5 X 2
O Fill in the missing numbers.

a) X 1.2 = 2.4 b) 3.1 X = 9.3 c) 2.2 X = 8.8
d) X 6 = 6.66 e) X 4= 12.8 f) X 5 = 12.25

0 Sue says that 2.34 X 2 = 4.68.
Chris says that 2.34 x 2 = 46.8.
Who is correct? Give a reason for your answer.