PSLE
Dana had jigsaw puzzles for sale. In the morning, she sold ²₅ of the jigsaw puzzles. In the afternoon, she sold ⁴₉ of the remaining jigsaw puzzles. After that, there were 100 jigsaw puzzles left. How many jigsaw puzzles did Dana have at first?
Fraction of jigsaw puzzles left after selling in the morning
= 1 - ²₅
= ³₅

Fraction of the remaining jigsaw puzzles after selling in the afternoon
= 1 - ⁴₉
= ⁵₉

⁵₉ of remaining jigsaw puzzles = 100
¹₉ of remaining jigsaw puzzles = 100 ÷ 5 = 20
⁹₉ of remaining jigsaw puzzles = 9 x 20 = 180

³₅ of total jigsaw puzzles = 180
²₅ of the total jigsaw puzzles = 180 ÷ 3 = 60
⁵₅ of the total jigsaw puzzles = 5 x 60 = 300

Number of jigsaw puzzles at first = 300

Answer(s): 300