PSLE
Harry had red staplers and yellow staplers for sale. He sold 240 red staplers. 40% of the staplers sold were yellow.

1. How many red staplers and yellow staplers did Harry sell altogether?
2. He sold 50% of his staplers. 70% of the staplers left unsold were red. How many yellow staplers did Harry have at first?

	Red	Yellow	Total	Total in percent
Before	6.5 u	3.5 u	10 u	100%
Change	- 60% - 3 u	- 40% - 2 u	- 100% - 5 u	- 50%
After	70% 3.5 u	30% 1.5 u	100% 5 u	50%

40% = ⁴⁰₁₀₀ = ²₅

Total number of staplers sold = 5 u
Number of yellow staplers sold = 2 u

Number of red staplers sold
= 5 u - 2 u
= 3 u

3 u = 240

1 u = 240 ÷ 3 = 80

Total number of staplers sold
= 5 u
= 5 x 80
= 400

(b)
Percent of the staplers left unsold
= 100% - 50%
= 50%

50% of the staplers that were sold = 5 u
50% of the staplers that were left unsold = 5 u

Percent of the staplers left unsold that were red = 70%
Percent of the staplers left unsold that were yellow = 100% - 70% = 30%

Number of the staplers left unsold that were yellow
= 30% x 5 u
= ³⁰₁₀₀ x 5 u
= 1.5 u

Number of yellow staplers that Harry had at first
= 1.5 u + 2 u
= 3.5 u
= 3.5 x 80
= 280

Answer(s): (a) 400; (b) 280