PSLE
Henry had a collection of post-it pads, markers and glues. He had 17 post-it pads. 40% of his collection was markers. He had 10 fewer markers than glues.

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

(a)
40% = ⁴⁰₁₀₀ = ²₅

Number of markers = 2 u
Number of glues = 2 u + 10
Number of post-it pads = 17
Total number of items = 5 u

5 u = 2 u + 2 u + 10 + 17
5 u - 4 u = 27
1 u = 27

Number of markers
= 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 markers
= 80% x 135
= ⁸⁰₁₀₀ x 135
= 108

Number of glues and post-it pads
= 5 u - 2 u
= 3 u
= 3 x 27
= 81

Number of markers left
= 108 - 81
= 27

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

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