PSLE
Wesley had a collection of correction tapes, notebooks and rulers. He had 277 correction tapes. 15% of his collection was notebooks. He had 31 fewer notebooks than rulers.

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

(a)
15% = ¹⁵₁₀₀ = ³₂₀

Number of notebooks = 3 u
Number of rulers = 3 u + 31
Number of correction tapes = 277
Total number of items = 20 u

20 u = 3 u + 3 u + 31 + 277
20 u - 6 u = 308
14 u = 308

1 u = 308 ÷ 14 = 22

Number of notebooks
= 3 u
= 3 x 22
= 66

(b)
Total number of items at first
= 20 u
= 20 x 22
= 440

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

Number of items after giving away some notebooks
= 80% x 440
= ⁸⁰₁₀₀ x 440
= 352

Number of rulers and correction tapes
= 20 u - 3 u
= 17 u
= 17 x 22
= 374

Number of notebooks left
= 352 - 374
= 22

Percentage of his collection that was notebooks after that
= ²²₃₅₂ x 100%
= 6.25%

Answer(s): (a) 66; (b) 6.25%