PSLE
Kathy baked some biscuits. She gave ¹₁₀ of the biscuits to her relatives and 76 to her friends. She was left with ¹₂ of the biscuits. She packed these into 12 boxes. Some boxes contained 5 biscuits while the rest contained 10 biscuits.

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

(a)
Fraction of the biscuits given to her friends
= 1 - ¹₁₀ - ¹₂

= 1 - ¹₁₀ - ⁵₁₀
= ⁴₁₀

Number of biscuits that Kathy gave to her friends = 4 u

4 u = 76

1 u = 76 ÷ 4 = 19

Number of biscuits that were packed in 12 boxes
= 5 u
= 5 x 19
= 95

Number of biscuits that were packed in 12 boxes = 95

Boxes of 10	Biscuits	Boxes of 5	Biscuits	Total biscuits
12	120	0	0	120
11	110	1	5	115

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

Small difference
= 120 - 115
= 5

Big difference
= 120 - 95
= 25

Number of boxes of 5 biscuits 
= 25 ÷ 5
= 5

Number of boxes of 10 biscuits
= 12 - 5
= 7

Answer(s): (a) 95; (b) 7