New
New
Year 5

Multiply 1-digit numbers by decimals

I can explain how to use multiplying and dividing by 10 or 100 to multiply 1-digit numbers by decimal fractions.

New
New
Year 5

Multiply 1-digit numbers by decimals

I can explain how to use multiplying and dividing by 10 or 100 to multiply 1-digit numbers by decimal fractions.

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Lesson details

Key learning points

  1. Use place value to convert the decimal fraction by multiplication to a whole number.
  2. Use unitising, known facts and/or the distributive law to multiply the whole numbers.
  3. Use place value to convert the number by division to adjust the product.

Keywords

  • Unitising - Treating groups that contain the same number of things as ‘ones’ or ‘units’. It is important particularly in handling money and in understanding place value and supports us to think multiplicatively.

  • Distributive law - The distributive law says that multiplying a number by a group of numbers added together is the same as doing each multiplication separately.

Common misconception

Children may scale the decimal fraction inaccurately or may forget to scale the product accordingly to solve the original equation.

If a decimal fraction has only tenths, we multiply by 10 to form a whole number. If the decimal fraction has hundredths, we multiply by 100 to form a whole number. Remember to adjust the product to answer the original equation.

Provide scaffolds for those who are not confident with their times tables to avoid overload. Children should already be aware of the distributive law but it may be an idea to revisit this prior to the lesson to ensure children are confident with the concept. Stick to mental methods of calculation.
Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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6 Questions

Q1.
Count up in 25s. What would come next? 25, 50,
Correct Answer: 75
Q2.
Match the factors to their product.
Correct Answer:3 × 10 =,30

30

Correct Answer:14 × 10 =,140

140

Correct Answer:103 × 10 =,1030

1030

Correct Answer:2.1 × 10 =,21

21

Correct Answer:0.5 × 10 =,5

5

Q3.
Match the expressions to their answer.
Correct Answer:40 × 0.1 ,4

4

Correct Answer:150 × 0.1 ,15

15

Correct Answer:15 × 0.1 ,1.5

1.5

Correct Answer:4 × 0.1 ,0.4

0.4

Correct Answer:0.4 × 0.1 ,0.04

0.04

Q4.
Match the equivalent expressions.
Correct Answer:53 × 0.1,53 ÷ 10

53 ÷ 10

Correct Answer:5 × 0.01,53 ÷ 100

53 ÷ 100

Correct Answer:53 × 1,53 ÷ 1

53 ÷ 1

Correct Answer:5.3 × 0.1,5.3 ÷ 10

5.3 ÷ 10

Correct Answer:5.3 × 0.01,5.3 ÷ 100

5.3 ÷ 100

Q5.
Lucas has 1.8 kg flour. Sofia has one-tenth times this amount. How much flour does Sofia have? kg
Correct Answer: 0.18, 0.18 kg
Q6.
Sofia’s flower is 87 cm tall. Lucas’ has only grown to one-hundredth times this height. How tall is Lucas’ flower? cm
Correct Answer: 0.87, 0.87 cm

6 Questions

Q1.
If 9 × 14 = 126, what does 9 × 1.4 equal?
126
Correct answer: 12.6
1.26
0.126
Q2.
Calculate 9 × 2.5 =
Correct Answer: 22.5
Q3.
Use unitising and known facts to match the equation to its product.
Correct Answer:0.04 × 8 =,0.32

0.32

Correct Answer:0.07 × 6 =,0.42

0.42

Correct Answer:0.9 × 5 =,4.5

4.5

Correct Answer:4 × 0.3 =,1.2

1.2

Correct Answer:3 × 0.8 =,2.4

2.4

Q4.
Calculate this: 3 × 8.7 =
Correct Answer: 26.1
Q5.
Plums cost £2.35 per kilogram. Sofia buys 4 kilograms of strawberries. How much does she spend? £
Correct Answer: 9.40, £9.40
Q6.
Sofia buys eight stickers. They cost £0.52 each. How much do they cost altogether? £
Correct Answer: 4.16, £4.16