PSLE
Riordan had red staplers and purple staplers for sale. He sold 270 red staplers. 70% of the staplers sold were purple.

1. How many red staplers and purple staplers did Riordan sell altogether?
2. He sold 50% of his staplers. 75% of the staplers left unsold were red. How many purple staplers did Riordan have at first?

	Red	Purple	Total	Total in percent
Before	10.5 u	9.5 u	20 u	100%
Change	- 30% - 3 u	- 70% - 7 u	- 100% - 10 u	- 50%
After	75% 7.5 u	25% 2.5 u	100% 10 u	50%

70% = ⁷⁰₁₀₀ = ⁷₁₀

Total number of staplers sold = 10 u
Number of purple staplers sold = 7 u

Number of red staplers sold
= 10 u - 7 u
= 3 u

3 u = 270

1 u = 270 ÷ 3 = 90

Total number of staplers sold
= 10 u
= 10 x 90
= 900

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

50% of the staplers that were sold = 10 u
50% of the staplers that were left unsold = 10 u

Percent of the staplers left unsold that were red = 75%
Percent of the staplers left unsold that were purple = 100% - 75% = 25%

Number of the staplers left unsold that were purple
= 25% x 10 u
= ²⁵₁₀₀ x 10 u
= 2.5 u

Number of purple staplers that Riordan had at first
= 2.5 u + 7 u
= 9.5 u
= 9.5 x 90
= 855

Answer(s): (a) 900; (b) 855