PSLE
Ben had a collection of highlighters, pencils and foolscaps. He had 13 highlighters. 40% of his collection was pencils. He had 14 fewer pencils than foolscaps.

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

(a)
40% = ⁴⁰₁₀₀ = ²₅

Number of pencils = 2 u
Number of foolscaps = 2 u + 14
Number of highlighters = 13
Total number of items = 5 u

5 u = 2 u + 2 u + 14 + 13
5 u - 4 u = 27
1 u = 27

Number of pencils
= 2 u
= 2 x 27
= 54

(b)
Total number of items at first
= 5 u
= 5 x 27
= 135

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

Number of items after giving away some pencils
= 80% x 135
= ⁸⁰₁₀₀ x 135
= 108

Number of foolscaps and highlighters
= 5 u - 2 u
= 3 u
= 3 x 27
= 81

Number of pencils left
= 108 - 81
= 27

Percentage of his collection that was pencils after that
= ²⁷₁₀₈ x 100%
= 25%

Answer(s): (a) 54; (b) 25%