PSLE
Carl had purple staplers and orange staplers for sale. He sold 70 purple staplers. 30% of the staplers sold were orange.

1. How many purple staplers and orange staplers did Carl sell altogether?
2. He sold 50% of his staplers. 80% of the staplers left unsold were purple. How many orange staplers did Carl have at first?

	Purple	Orange	Total	Total in percent
Before	15 u	5 u	20 u	100%
Change	- 70% - 7 u	- 30% - 3 u	- 100% - 10 u	- 50%
After	80% 8 u	20% 2 u	100% 10 u	50%

30% = ³⁰₁₀₀ = ³₁₀

Total number of staplers sold = 10 u
Number of orange staplers sold = 3 u

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

7 u = 70

1 u = 70 ÷ 7 = 10

Total number of staplers sold
= 10 u
= 10 x 10
= 100

(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 purple = 80%
Percent of the staplers left unsold that were orange = 100% - 80% = 20%

Number of the staplers left unsold that were orange
= 20% x 10 u
= ²⁰₁₀₀ x 10 u
= 2 u

Number of orange staplers that Carl had at first
= 2 u + 3 u
= 5 u
= 5 x 10
= 50

Answer(s): (a) 100; (b) 50