PSLE
Andy had a collection of folders, staplers and correction tapes. He had 313 folders. 15% of his collection was staplers. He had 37 fewer staplers than correction tapes.

1. How many staplers did Andy have?
2. Andy 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 correction tapes = 3 u + 37
Number of folders = 313
Total number of items = 20 u

20 u = 3 u + 3 u + 37 + 313
20 u - 6 u = 350
14 u = 350

1 u = 350 ÷ 14 = 25

Number of staplers
= 3 u
= 3 x 25
= 75

(b)
Total number of items at first
= 20 u
= 20 x 25
= 500

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

Number of items after giving away some staplers
= 80% x 500
= ⁸⁰₁₀₀ x 500
= 400

Number of correction tapes and folders
= 20 u - 3 u
= 17 u
= 17 x 25
= 425

Number of staplers left
= 400 - 425
= 25

Percentage of his collection that was staplers after that
= ²⁵₄₀₀ x 100%
= 6.25%

Answer(s): (a) 75; (b) 6.25%