PSLE
Yen baked some biscuits. She gave ¹₁₀ of the biscuits to her friends and 124 to her relatives. She was left with ¹₂ of the biscuits. She packed these into 19 boxes. Some boxes contained 5 biscuits while the rest contained 10 biscuits.

1. How many biscuits were packed into the 19 boxes?
2. How many boxes contained 10 biscuits?

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

= 1 - ¹₁₀ - ⁵₁₀
= ⁴₁₀

Number of biscuits that Yen gave to her relatives = 4 u

4 u = 124

1 u = 124 ÷ 4 = 31

Number of biscuits that were packed in 19 boxes
= 5 u
= 5 x 31
= 155

Number of biscuits that were packed in 19 boxes = 155

Boxes of 10	Biscuits	Boxes of 5	Biscuits	Total biscuits
19	190	0	0	190
18	180	1	5	185

If all the biscuits are packed in boxes of 10, the number of biscuits needed
= 19 x 10
= 190

Small difference
= 190 - 185
= 5

Big difference
= 190 - 155
= 35

Number of boxes of 5 biscuits 
= 35 ÷ 5
= 7

Number of boxes of 10 biscuits
= 19 - 7
= 12

Answer(s): (a) 155; (b) 12