PSLE
Mr Lau used ⁷₉ of his money to buy 15 starfruits and 6 passion fruits. The cost of 5 starfruits was the same as that of 3 passion fruits. What was the most number of passion fruits that Mr Lau could buy with the money he had left?
Fraction of his money that he had left
= 1 - ⁷₉ 
= ²₉

Let the cost of 1 starfruit be 1 S.
Let the cost of 1 passion fruit be 1 P.

5 S = 3 P _(x3)
15 S = 9 P

Since Mr Lau wants to buy passion fruits with the money he had left, 15 starfruits will be substituted as 9 passion fruits.

⁷₉ of his money
= 15 S + 6 P
= 9 P + 6 P
= 15 P

⁷₉ of his money → 15 P
¹₉ of his money → ¹⁵₇ P
²₉ of his money → 2 x ¹⁵₇ P = 4²₇ P

Maximum number of passion fruits he could buy with the money that he had left = 4

Answer(s): 4