PSLE
Dana baked some cupcakes. She gave ¹₅ of the cupcakes to her relatives and 75 to her friends. She was left with ¹₂ of the cupcakes. She packed these into 15 boxes. Some boxes contained 7 cupcakes while the rest contained 9 cupcakes.

1. How many cupcakes were packed into the 15 boxes?
2. How many boxes contained 9 cupcakes?

(a)
Fraction of the cupcakes given to her friends
= 1 - ¹₅ - ¹₂

= 1 - ²₁₀ - ⁵₁₀
= ³₁₀

Number of cupcakes that Dana gave to her friends = 3 u

3 u = 75

1 u = 75 ÷ 3 = 25

Number of cupcakes that were packed in 15 boxes
= 5 u
= 5 x 25
= 125

Number of cupcakes that were packed in 15 boxes = 125

Boxes of 9	Cupcakes	Boxes of 7	Cupcakes	Total cupcakes
15	135	0	0	135
14	126	1	7	133

If all the cupcakes are packed in boxes of 9, the number of cupcakes needed
= 15 x 9
= 135

Small difference
= 135 - 133
= 2

Big difference
= 135 - 125
= 10

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

Number of boxes of 9 cupcakes
= 15 - 5
= 10

Answer(s): (a) 125; (b) 10