PSLE
Fred had a collection of notebooks, markers and correction tapes. He had 160 notebooks. 15% of his collection was markers. He had 50 fewer markers than correction tapes.

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

(a)
15% = ¹⁵₁₀₀ = ³₂₀

Number of markers = 3 u
Number of correction tapes = 3 u + 50
Number of notebooks = 160
Total number of items = 20 u

20 u = 3 u + 3 u + 50 + 160
20 u - 6 u = 210
14 u = 210

1 u = 210 ÷ 14 = 15

Number of markers
= 3 u
= 3 x 15
= 45

(b)
Total number of items at first
= 20 u
= 20 x 15
= 300

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

Number of items after giving away some markers
= 80% x 300
= ⁸⁰₁₀₀ x 300
= 240

Number of correction tapes and notebooks
= 20 u - 3 u
= 17 u
= 17 x 15
= 255

Number of markers left
= 240 - 255
= 15

Percentage of his collection that was markers after that
= ¹⁵₂₄₀ x 100%
= 6.25%

Answer(s): (a) 45; (b) 6.25%