PSLE
Mr Ma used ⁵₇ of his money to buy 15 pomegranates and 9 mangosteens. The cost of 5 pomegranates was the same as that of 4 mangosteens. What was the most number of mangosteens that Mr Ma could buy with the money he had left?
Fraction of his money that he had left
= 1 - ⁵₇ 
= ²₇

Let the cost of 1 pomegranate be 1 P.
Let the cost of 1 mangosteen be 1 M.

5 P = 4 M _(x3)
15 P = 12 M

Since Mr Ma wants to buy mangosteens with the money he had left, 15 pomegranates will be substituted as 12 mangosteens.

⁵₇ of his money
= 15 P + 9 M
= 12 M + 9 M
= 21 M

⁵₇ of his money → 21 M
¹₇ of his money → ²¹₅ M
²₇ of his money → 2 x ²¹₅ M = 8²₅ M

Maximum number of mangosteens he could buy with the money that he had left = 8

Answer(s): 8