PSLE
Pierre had a collection of staplers, correction tapes and highlighters. He had 17 staplers. 40% of his collection was correction tapes. He had 13 fewer correction tapes than highlighters.

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

(a)
40% = ⁴⁰₁₀₀ = ²₅

Number of correction tapes = 2 u
Number of highlighters = 2 u + 13
Number of staplers = 17
Total number of items = 5 u

5 u = 2 u + 2 u + 13 + 17
5 u - 4 u = 30
1 u = 30

Number of correction tapes
= 2 u
= 2 x 30
= 60

(b)
Total number of items at first
= 5 u
= 5 x 30
= 150

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

Number of items after giving away some correction tapes
= 80% x 150
= ⁸⁰₁₀₀ x 150
= 120

Number of highlighters and staplers
= 5 u - 2 u
= 3 u
= 3 x 30
= 90

Number of correction tapes left
= 120 - 90
= 30

Percentage of his collection that was correction tapes after that
= ³⁰₁₂₀ x 100%
= 25%

Answer(s): (a) 60; (b) 25%