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Year 7

Checking and securing finding a fraction of a given amount

I can find a fraction of a given amount.

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New
New
Year 7

Checking and securing finding a fraction of a given amount

I can find a fraction of a given amount.

Download all resources
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Share activities with pupils
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Lesson details

Key learning points

  1. The given amount is multiplied by the fraction.
  2. The given amount may be given in a variety of forms.
  3. A bar model can represent this situation.

Keywords

  • Reciprocal - The reciprocal is the multiplicative inverse of any non-zero number. Any non-zero number multiplied by its reciprocal is equal to 1.

Common misconception

An assumption that you cannot find a fraction greater than 1 of an amount.

Recognising that 'of' and multiplication are equivalent should help with this , as pupils are familiar with multiplying fractions.

During the efficient methods part of the lesson, challenge pupils to come up with their own examples for each category on mini-whiteboards. This will help reinforce the idea of checking if the denominator is a factor of the 'amount'.
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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Starter quiz

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6 Questions

Q1.
Match the equivalent ratios.
Correct Answer:4 : 5,12 : 15

12 : 15

Correct Answer:4 : 3,16 : 12

16 : 12

Correct Answer:3 : 4,15 : 20

15 : 20

Correct Answer:5 : 4,60 : 48

60 : 48

Correct Answer:5 : 3,25 : 15

25 : 15

Correct Answer:3 : 5,24 : 40

24 : 40

Q2.
What symbol separates the parts of a ratio? E.g. the mathematical notation for writing 4 to 5.
Correct Answer: :, colon
Q3.
Simplify 24 : 36
Correct Answer: 2 : 3, 2:3, 2 to 3
Q4.
In a bag there are only triangles and squares. The ratio of triangles to squares is 3 : 1. There are 60 shapes in total. Who correctly worked out the number of squares?
Alex "60 triangles, so there are 20 squares because of the ratio is 3 : 1"
Laura "180 triangles, so there are 40 squares because of the ratio is 3 : 1"
Andeep "20 triangles, so there are 40 squares because of the ratio is 4 : 1"
Correct answer: Sofia "45 triangles, so there are 15 squares because of the ratio is 4 : 1"
Jun "34 triangles, so there are 26 squares because of the ratio is 4 : 1"
Q5.
Chocolates in a box either have red or blue wrappers. The ratio of red to blue is 5 : 4. If the difference between the red and blue chocolates is 3, how many chocolates are in the box?
Correct Answer: 27, 27 chocolates, twenty seven, twenty-seven, twentyseven
Q6.
Chocolates in a box either have red or blue wrappers. The ratio of red to blue is 3 : 2. Andeep eats 2 blue chocolates and now the ratio is 12 : 7. How many blues were in the box originally?
Correct Answer: 16, 16 chocolates, sixteen, sixteen chocolates

Exit quiz

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6 Questions

Q1.
Which of the following is not the reciprocal of 4?
$$1\over4$$
$$5\over20$$
$$8\over32$$
Correct answer: $$9\over35$$
$$11\over44$$
Q2.
Use a bar model to calculate $$3\over8$$ of 48
Correct Answer: 18, eighteen
Q3.
Calculate 60 × $$3\over5$$
Correct Answer: 36, thirty-six, thirty six, thirtysix
Q4.
Which of the following are equivalent calculations for $$5\over9$$ of 72?
Correct answer: 72 × $$5\over9$$
Correct answer: (72 ÷ 9) × 5
(72 ÷ 5) × 9
Correct answer: $$5\over9$$ × $${8\times9}\over{1}$$
Correct answer: $$72\over9$$ × 5
Q5.
Calculate $$2 {{3} \over {5}}$$ × $$2\over7$$
$$16\over35$$
Correct answer: $$26\over35$$
$$36\over35$$
$$46\over35$$
Q6.
Find $$12 {{3} \over {5}}$$ of 25
Correct Answer: 315