PSLE
Ben had a collection of highlighters, staplers and folders. He had 193 highlighters. 15% of his collection was staplers. He had 45 fewer staplers than folders.

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

(a)
15% = ¹⁵₁₀₀ = ³₂₀

Number of staplers = 3 u
Number of folders = 3 u + 45
Number of highlighters = 193
Total number of items = 20 u

20 u = 3 u + 3 u + 45 + 193
20 u - 6 u = 238
14 u = 238

1 u = 238 ÷ 14 = 17

Number of staplers
= 3 u
= 3 x 17
= 51

(b)
Total number of items at first
= 20 u
= 20 x 17
= 340

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

Number of items after giving away some staplers
= 80% x 340
= ⁸⁰₁₀₀ x 340
= 272

Number of folders and highlighters
= 20 u - 3 u
= 17 u
= 17 x 17
= 289

Number of staplers left
= 272 - 289
= 17

Percentage of his collection that was staplers after that
= ¹⁷₂₇₂ x 100%
= 6.25%

Answer(s): (a) 51; (b) 6.25%