PSLE
Mr Choo used ³₈ of his money to buy 8 starfruits and 7 persimmons. The cost of 4 starfruits was the same as that of 2 persimmons. What was the most number of persimmons that Mr Choo could buy with the money he had left?
Fraction of his money that he had left
= 1 - ³₈ 
= ⁵₈

Let the cost of 1 starfruit be 1 S.
Let the cost of 1 persimmon be 1 P.

4 S = 2 P _(x2)
8 S = 4 P

Since Mr Choo wants to buy persimmons with the money he had left, 8 starfruits will be substituted as 4 persimmons.

³₈ of his money
= 8 S + 7 P
= 4 P + 7 P
= 11 P

³₈ of his money → 11 P
¹₈ of his money → ¹¹₃ P
⁵₈ of his money → 5 x ¹¹₃ P = 18¹₃ P

Maximum number of persimmons he could buy with the money that he had left = 18

Answer(s): 18