PSLE
Barbara baked some biscuits. She gave ²₅ of the biscuits to her relatives and 80 to her friends. She was left with ⁷₂₀ of the biscuits. She packed these into 17 boxes. Some boxes contained 4 biscuits while the rest contained 8 biscuits.

1. How many biscuits were packed into the 17 boxes?
2. How many boxes contained 8 biscuits?

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

= 1 - ⁸₂₀ - ⁷₂₀
= ⁵₂₀

Number of biscuits that Barbara gave to her friends = 5 u

5 u = 80

1 u = 80 ÷ 5 = 16

Number of biscuits that were packed in 17 boxes
= 7 u
= 7 x 16
= 112

Number of biscuits that were packed in 17 boxes = 112

Boxes of 8	Biscuits	Boxes of 4	Biscuits	Total biscuits
17	136	0	0	136
16	128	1	4	132

If all the biscuits are packed in boxes of 8, the number of biscuits needed
= 17 x 8
= 136

Small difference
= 136 - 132
= 4

Big difference
= 136 - 112
= 24

Number of boxes of 4 biscuits 
= 24 ÷ 4
= 6

Number of boxes of 8 biscuits
= 17 - 6
= 11

Answer(s): (a) 112; (b) 11