PSLE
David had a collection of correction tapes, punchers and staplers. He had 57 correction tapes. 30% of his collection was punchers. He had 43 fewer punchers than staplers.

1. How many punchers did David have?
2. David gave away some punchers. His total collection decreased by 20%. What percentage of his collection was punchers after that?

(a)
30% = ³⁰₁₀₀ = ³₁₀

Number of punchers = 3 u
Number of staplers = 3 u + 43
Number of correction tapes = 57
Total number of items = 10 u

10 u = 3 u + 3 u + 43 + 57
10 u - 6 u = 100
4 u = 100

1 u = 100 ÷ 4 = 25

Number of punchers
= 3 u
= 3 x 25
= 75

(b)
Total number of items at first
= 10 u
= 10 x 25
= 250

Total collection in the end in percent
= 100% - 20%
= 80%

Number of items after giving away some punchers
= 80% x 250
= ⁸⁰₁₀₀ x 250
= 200

Number of staplers and correction tapes
= 10 u - 3 u
= 7 u
= 7 x 25
= 175

Number of punchers left
= 200 - 175
= 25

Percentage of his collection that was punchers after that
= ²⁵₂₀₀ x 100%
= 12.5%

Answer(s): (a) 75; (b) 12.5%