PSLE
Asher had a collection of pencils, files and foolscaps. He had 375 pencils. 15% of his collection was files. He had 17 fewer files than foolscaps.

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

(a)
15% = ¹⁵₁₀₀ = ³₂₀

Number of files = 3 u
Number of foolscaps = 3 u + 17
Number of pencils = 375
Total number of items = 20 u

20 u = 3 u + 3 u + 17 + 375
20 u - 6 u = 392
14 u = 392

1 u = 392 ÷ 14 = 28

Number of files
= 3 u
= 3 x 28
= 84

(b)
Total number of items at first
= 20 u
= 20 x 28
= 560

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

Number of items after giving away some files
= 80% x 560
= ⁸⁰₁₀₀ x 560
= 448

Number of foolscaps and pencils
= 20 u - 3 u
= 17 u
= 17 x 28
= 476

Number of files left
= 448 - 476
= 28

Percentage of his collection that was files after that
= ²⁸₄₄₈ x 100%
= 6.25%

Answer(s): (a) 84; (b) 6.25%