PSLE
Irene baked some cupcakes. She gave ²₅ of the cupcakes to her relatives and 80 to her friends. She was left with ⁷₂₀ of the cupcakes. She packed these into 12 boxes. Some boxes contained 8 cupcakes while the rest contained 10 cupcakes.

1. How many cupcakes were packed into the 12 boxes?
2. How many boxes contained 10 cupcakes?

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

= 1 - ⁸₂₀ - ⁷₂₀
= ⁵₂₀

Number of cupcakes that Irene gave to her friends = 5 u

5 u = 80

1 u = 80 ÷ 5 = 16

Number of cupcakes that were packed in 12 boxes
= 7 u
= 7 x 16
= 112

Number of cupcakes that were packed in 12 boxes = 112

Boxes of 10	Cupcakes	Boxes of 8	Cupcakes	Total cupcakes
12	120	0	0	120
11	110	1	8	118

If all the cupcakes are packed in boxes of 10, the number of cupcakes needed
= 12 x 10
= 120

Small difference
= 120 - 118
= 2

Big difference
= 120 - 112
= 8

Number of boxes of 8 cupcakes 
= 8 ÷ 2
= 4

Number of boxes of 10 cupcakes
= 12 - 4
= 8

Answer(s): (a) 112; (b) 8