PSLE
Mark had yellow staplers and silver staplers for sale. He sold 180 yellow staplers. 40% of the staplers sold were silver.

1. How many yellow staplers and silver staplers did Mark sell altogether?
2. He sold 50% of his staplers. 60% of the staplers left unsold were yellow. How many silver staplers did Mark have at first?

	Yellow	Silver	Total	Total in percent
Before	6 u	4 u	10 u	100%
Change	- 60% - 3 u	- 40% - 2 u	- 100% - 5 u	- 50%
After	60% 3 u	40% 2 u	100% 5 u	50%

40% = ⁴⁰₁₀₀ = ²₅

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

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

3 u = 180

1 u = 180 ÷ 3 = 60

Total number of staplers sold
= 5 u
= 5 x 60
= 300

(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 yellow = 60%
Percent of the staplers left unsold that were silver = 100% - 60% = 40%

Number of the staplers left unsold that were silver
= 40% x 5 u
= ⁴⁰₁₀₀ x 5 u
= 2 u

Number of silver staplers that Mark had at first
= 2 u + 2 u
= 4 u
= 4 x 60
= 240

Answer(s): (a) 300; (b) 240