J's answer to Luana's Primary 5 Maths Percentage Singapore question.

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J
J's answer
1022 answers (A Helpful Person)
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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