PSLE
Gillian baked some puffs. She gave ²₅ of the puffs to her students and 50 to her friends. She was left with ⁷₂₀ of the puffs. She packed these into 10 boxes. Some boxes contained 4 puffs while the rest contained 9 puffs.

1. How many puffs were packed into the 10 boxes?
2. How many boxes contained 9 puffs?

(a)
Fraction of the puffs given to her friends
= 1 - ²₅ - ⁷₂₀

= 1 - ⁸₂₀ - ⁷₂₀
= ⁵₂₀

Number of puffs that Gillian gave to her friends = 5 u

5 u = 50

1 u = 50 ÷ 5 = 10

Number of puffs that were packed in 10 boxes
= 7 u
= 7 x 10
= 70

Number of puffs that were packed in 10 boxes = 70

Boxes of 9	Puffs	Boxes of 4	Puffs	Total puffs
10	90	0	0	90
9	81	1	4	85

If all the puffs are packed in boxes of 9, the number of puffs needed
= 10 x 9
= 90

Small difference
= 90 - 85
= 5

Big difference
= 90 - 70
= 20

Number of boxes of 4 puffs 
= 20 ÷ 5
= 4

Number of boxes of 9 puffs
= 10 - 4
= 6

Answer(s): (a) 70; (b) 6