PSLE
Mr Song used ⁴₇ of his money to buy 9 chikoos and 10 starfruits. The cost of 3 chikoos was the same as that of 4 starfruits. What was the most number of starfruits that Mr Song could buy with the money he had left?
Fraction of his money that he had left
= 1 - ⁴₇ 
= ³₇

Let the cost of 1 chikoo be 1 C.
Let the cost of 1 starfruit be 1 S.

3 C = 4 S _(x3)
9 C = 12 S

Since Mr Song wants to buy starfruits with the money he had left, 9 chikoos will be substituted as 12 starfruits.

⁴₇ of his money
= 9 C + 10 S
= 12 S + 10 S
= 22 S

⁴₇ of his money → 22 S
¹₇ of his money → ²²₄ S
³₇ of his money → 3 x ²²₄ S = 16²₄ S

Maximum number of starfruits he could buy with the money that he had left = 16

Answer(s): 16