PSLE
Risa baked some scones. She gave ¹₅ of the scones to her students and 126 to her friends. She was left with ⁷₂₀ of the scones. She packed these into 12 boxes. Some boxes contained 7 scones while the rest contained 9 scones.

1. How many scones were packed into the 12 boxes?
2. How many boxes contained 9 scones?

(a)
Fraction of the scones given to her friends
= 1 - ¹₅ - ⁷₂₀

= 1 - ⁴₂₀ - ⁷₂₀
= ⁹₂₀

Number of scones that Risa gave to her friends = 9 u

9 u = 126

1 u = 126 ÷ 9 = 14

Number of scones that were packed in 12 boxes
= 7 u
= 7 x 14
= 98

Number of scones that were packed in 12 boxes = 98

Boxes of 9	Scones	Boxes of 7	Scones	Total scones
12	108	0	0	108
11	99	1	7	106

If all the scones are packed in boxes of 9, the number of scones needed
= 12 x 9
= 108

Small difference
= 108 - 106
= 2

Big difference
= 108 - 98
= 10

Number of boxes of 7 scones 
= 10 ÷ 2
= 5

Number of boxes of 9 scones
= 12 - 5
= 7

Answer(s): (a) 98; (b) 7