PSLE
Peter had a collection of post-it pads, highlighters and foolscaps. He had 17 post-it pads. 40% of his collection was highlighters. He had 12 fewer highlighters than foolscaps.

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

(a)
40% = ⁴⁰₁₀₀ = ²₅

Number of highlighters = 2 u
Number of foolscaps = 2 u + 12
Number of post-it pads = 17
Total number of items = 5 u

5 u = 2 u + 2 u + 12 + 17
5 u - 4 u = 29
1 u = 29

Number of highlighters
= 2 u
= 2 x 29
= 58

(b)
Total number of items at first
= 5 u
= 5 x 29
= 145

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

Number of items after giving away some highlighters
= 80% x 145
= ⁸⁰₁₀₀ x 145
= 116

Number of foolscaps and post-it pads
= 5 u - 2 u
= 3 u
= 3 x 29
= 87

Number of highlighters left
= 116 - 87
= 29

Percentage of his collection that was highlighters after that
= ²⁹₁₁₆ x 100%
= 25%

Answer(s): (a) 58; (b) 25%