Decimals And Ratio Worksheet (Page 3 of 13) in pdf

5 Work out

14 Work out the area of each shape.

Q5 hint

27 cm

a 3.7 × 2.2

b 2.5 × 4.2

c 7.22 × 3.1

Estimate ﬁ rst.

d 3.46 × 8.9

e 8.94 × 0.32

f 4.04 × 8.2

0.1 m

Discussion

10.4 cm

For each part, count the number of digits after the

decimal point in both numbers in the question.

0.1 m

Do the same for the answer. What do you notice?

7.9 cm

11.6 m

Real

A car can travel 13.8 kilometres on 1 litre of petrol.

How far can it travel on 8.8 litres of petrol?

6.6 cm

23.6 m

7 Follow these steps to work out 3.26 × 5.12

a Estimate the answer.

7.4 cm

0.2 m

b Work out 326 × 512

c Decide where to position the decimal point.

6.8 cm

2.4 m

8 Use the multiplication facts given to work out the answers.

Q8a hint

a 12 × 17 = 204. Work out 1.2 × 1.7

Real / Problem-solving

Anita is planning to paint the walls of her

The answer will have the digits 204.

b 36 × 14 = 504. Work out 3.6 × 0.14

living room.

Where do you put the decimal point?

c 108 × 4 = 432. Work out 10.8 × 0.04

2.9 m

3.75 m

d 36 × 72 = 2592. Work out 0.36 × 7.2

0.7 m

0.6 m

window

9 Work out

door

a 36 × 0.1

b 36 ÷ 10

c 45 × 0.1

left wall

front wall

right wall

back wall

d 45 ÷ 10

e 107 × 0.1

f 107 ÷ 10

Anita needs 0.1 litres of paint to paint each 1 m

Discussion

What do you notice?

How much paint will she need to paint all the walls?

10 Work out

Explore

Does multiplying one number by another always make it

a 8.6 × 0.1

b 11.6 × 0.1

c 0.53 × 0.1

bigger?

Choose some sensible numbers to help you explore this situation.

11 a Copy and complete.

Then use what you have learned in this lesson to help you answer the

29 × 1 =

question.

29 × 0.1 =

17 Reﬂ ect Look back at Q5. At the end of this question you discussed a

29 × 0.01 =

mathematical ‘rule’.

Reasoning

What division calculation is equivalent to ‘× 0.01’?

The rule tells you where to put the decimal point in the answer when

multiplying decimals.

12 Work out

Write the ‘rule’ in your own words.

a 3621 × 0.01

b 4568 × 0.01

c 88.6 × 0.01

Why do you think the rule was at the end of the question and not at the

beginning?

d 11.6 × 0.01

e 534 × 0.01

f 683 × 0.01

What would you do to multiply two decimals, if you couldn’t remember

the rule?

Problem-solving

A factory makes 3.5 silk ﬂ owers every second.

a Each ﬂ ower uses 60.3 cm of silk.

How many metres of silk are used in one minute?

b Each ﬂ ower has a 0.325 m wire stem.

A hotel orders 275 silk ﬂ owers.

What length of wire is needed?

Topic links : Multiplying and dividing by 10 and 100, Metric measures, Area

139

Theta 2, Section 6.2

Unit 6

Decimals and ratio

140

Decimals And Ratio Worksheet Page 3

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