PSLE
Perry had a collection of staplers, glues and notebooks. He had 12 staplers. 40% of his collection was glues. He had 18 fewer glues than notebooks.

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

(a)
40% = ⁴⁰₁₀₀ = ²₅

Number of glues = 2 u
Number of notebooks = 2 u + 18
Number of staplers = 12
Total number of items = 5 u

5 u = 2 u + 2 u + 18 + 12
5 u - 4 u = 30
1 u = 30

Number of glues
= 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 glues
= 80% x 150
= ⁸⁰₁₀₀ x 150
= 120

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

Number of glues left
= 120 - 90
= 30

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

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