PSLE
Albert had a collection of pens, correction tapes and pencils. He had 18 pens. 40% of his collection was correction tapes. He had 10 fewer correction tapes than pencils.

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

(a)
40% = ⁴⁰₁₀₀ = ²₅

Number of correction tapes = 2 u
Number of pencils = 2 u + 10
Number of pens = 18
Total number of items = 5 u

5 u = 2 u + 2 u + 10 + 18
5 u - 4 u = 28
1 u = 28

Number of correction tapes
= 2 u
= 2 x 28
= 56

(b)
Total number of items at first
= 5 u
= 5 x 28
= 140

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

Number of items after giving away some correction tapes
= 80% x 140
= ⁸⁰₁₀₀ x 140
= 112

Number of pencils and pens
= 5 u - 2 u
= 3 u
= 3 x 28
= 84

Number of correction tapes left
= 112 - 84
= 28

Percentage of his collection that was correction tapes after that
= ²⁸₁₁₂ x 100%
= 25%

Answer(s): (a) 56; (b) 25%