New
New
Year 7
Checking and securing finding a fraction of a given amount
I can find a fraction of a given amount.
New
New
Year 7
Checking and securing finding a fraction of a given amount
I can find a fraction of a given amount.
Lesson details
Key learning points
- The given amount is multiplied by the fraction.
- The given amount may be given in a variety of forms.
- A bar model can represent this situation.
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.
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.
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).
Video
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Starter quiz
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6 Questions
Q1.
Match the equivalent ratios.
Correct Answer:4 : 5,12 : 15
4 : 5 -
12 : 15
Correct Answer:4 : 3,16 : 12
4 : 3 -
16 : 12
Correct Answer:3 : 4,15 : 20
3 : 4 -
15 : 20
Correct Answer:5 : 4,60 : 48
5 : 4 -
60 : 48
Correct Answer:5 : 3,25 : 15
5 : 3 -
25 : 15
Correct Answer:3 : 5,24 : 40
3 : 5 -
24 : 40
Q2.
What symbol separates the parts of a ratio? E.g. the mathematical notation for writing 4 to 5.
Correct Answer: :, colon
:, colon
Q3.
Simplify 24 : 36
Correct Answer: 2 : 3, 2:3, 2 to 3
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"
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
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
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: $$9\over35$$
$$9\over35$$
$$11\over44$$
Q2.
Use a bar model to calculate $$3\over8$$ of 48
Correct Answer: 18, eighteen
18, eighteen
Q3.
Calculate 60 × $$3\over5$$
Correct Answer: 36, thirty-six, thirty six, thirtysix
36, thirty-six, thirty six, thirtysix
Q4.
Which of the following are equivalent calculations for $$5\over9$$ of 72?
Correct answer: 72 × $$5\over9$$
72 × $$5\over9$$
Correct answer: (72 ÷ 9) × 5
(72 ÷ 9) × 5
(72 ÷ 5) × 9
Correct answer: $$5\over9$$ × $${8\times9}\over{1}$$
$$5\over9$$ × $${8\times9}\over{1}$$
Correct answer: $$72\over9$$ × 5
$$72\over9$$ × 5
Q5.
Calculate $$2 {{3} \over {5}}$$ × $$2\over7$$
$$16\over35$$
Correct answer: $$26\over35$$
$$26\over35$$
$$36\over35$$
$$46\over35$$
Q6.
Find $$12 {{3} \over {5}}$$ of 25
Correct Answer: 315
315