PSLE
Mr Song used ²₉ of his money to buy 9 oranges and 9 mangosteens. The cost of 3 oranges was the same as that of 2 mangosteens. What was the most number of mangosteens that Mr Song could buy with the money he had left?
Fraction of his money that he had left
= 1 - ²₉ 
= ⁷₉

Let the cost of 1 orange be 1 O.
Let the cost of 1 mangosteen be 1 M.

3 O = 2 M _(x3)
9 O = 6 M

Since Mr Song wants to buy mangosteens with the money he had left, 9 oranges will be substituted as 6 mangosteens.

²₉ of his money
= 9 O + 9 M
= 6 M + 9 M
= 15 M

²₉ of his money → 15 M
¹₉ of his money → ¹⁵₂ M
⁷₉ of his money → 7 x ¹⁵₂ M = 52¹₂ M

Maximum number of mangosteens he could buy with the money that he had left = 52

Answer(s): 52