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primary 5 | Maths | Percentage

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Date Posted: 5 months ago
Views: 74

132 books and magazines in total.
Since English books are 5/7 of total books,
We can let number of English books be 5 units, and non-English books be 2 units , a total of 7 units.
60% → 60/100 = 6/10 = 3/5
So we can let number of English magazines be 3 parts, and non-English magazines be 2 parts, a total of 5 parts.
Since there are 92 English books and magazines in total, total number of non-English magazines and books = 132 - 92 = 40
From the info about non-English books, we can deduce that:
2 units + 2 parts = 40
Then 1 unit + 1 part = 20
5 units + 5 parts = 100
Total number of books and magazines = 7 units + 5 parts = 132
132 = 2 units + 5 units + 5 parts
132 = 2 units + 100
From this we can deduce that 2 units = 132 - 100 = 32
1 unit = 32 ÷ 2 = 16
a)
Number of books = 7 units = 7 x 16 = 112
b)
1 part = 20 - 1 unit = 20 - 16 = 4
Number of English magazines = 3 parts
= 3 x 4 = 12
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Date Posted: 5 months ago
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Is this really a P5 problem?

Solved with some algebraic manipulation, which is, to the best of my knowledge, outside of the P5 syllabus.

Alternatively, guess and check may work, but will be very time consuming, as each possible answer has to be verified and eliminated accordingly.

To use guess and check, you will have to list out a combination of multiples of 7 and multiples of 10 that can add up to 132.
Date Posted: 5 months ago
J
5 months ago
It is usually called the unit-part method in PSLE syllabus. Drawing models to deduce the value of 1 part/unit is also employed
Diagram/model representation :
All Books : ⬛⬛⬛⬛⬛⬛⬛
All Magazines : ⬜⬜⬜⬜⬜
Total = 132

English books : ⬛⬛⬛⬛⬛
English magazines : ⬜⬜⬜
Total for English = 92

Non-English books : ⬛⬛
Non-English magazines : ⬜⬜
Total for non-English = 132 - 92 = 40
So ⬛⬛ + ⬜⬜ = 40
Then ⬛ + ⬜ = 40 ÷ 2 = 20
Then ⬛⬛⬛⬛⬛ + ⬜⬜⬜⬜⬜ = 20 x 5 = 100

From above we know
⬛⬛⬛⬛⬛⬛⬛ +⬜⬜⬜⬜⬜ = 132
⬛⬛⬛⬛⬛ + ⬜⬜⬜⬜⬜ + ⬛⬛ = 132
100 + ⬛⬛ = 132
So ⬛⬛ = 132 - 100 = 32
⬛ = 32 ÷ 2 = 16
⬜ = 20 - 16 = 4
a) all books = 7 × ⬛ = 7 × 16 = 112
b) English magazines = 3 × ⬜ = 3 x 4 = 12
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