PSLE
Esther had rubik's cubes for sale. In the morning, she sold ²₇ of the rubik's cubes. In the afternoon, she sold ²₅ of the remaining rubik's cubes. After that, there were 42 rubik's cubes left. How many rubik's cubes did Esther have at first?
Fraction of rubik's cubes left after selling in the morning
= 1 - ²₇
= ⁵₇

Fraction of the remaining rubik's cubes after selling in the afternoon
= 1 - ²₅
= ³₅

³₅ of remaining rubik's cubes = 42
¹₅ of remaining rubik's cubes = 42 ÷ 3 = 14
⁵₅ of remaining rubik's cubes = 5 x 14 = 70

⁵₇ of total rubik's cubes = 70
²₇ of the total rubik's cubes = 70 ÷ 5 = 14
⁷₇ of the total rubik's cubes = 7 x 14 = 98

Number of rubik's cubes at first = 98

Answer(s): 98