PSLE
Luke had a collection of markers, folders and glues. He had 13 markers. 40% of his collection was folders. He had 12 fewer folders than glues.

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

(a)
40% = ⁴⁰₁₀₀ = ²₅

Number of folders = 2 u
Number of glues = 2 u + 12
Number of markers = 13
Total number of items = 5 u

5 u = 2 u + 2 u + 12 + 13
5 u - 4 u = 25
1 u = 25

Number of folders
= 2 u
= 2 x 25
= 50

(b)
Total number of items at first
= 5 u
= 5 x 25
= 125

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

Number of items after giving away some folders
= 80% x 125
= ⁸⁰₁₀₀ x 125
= 100

Number of glues and markers
= 5 u - 2 u
= 3 u
= 3 x 25
= 75

Number of folders left
= 100 - 75
= 25

Percentage of his collection that was folders after that
= ²⁵₁₀₀ x 100%
= 25%

Answer(s): (a) 50; (b) 25%