PSLE
Luke had black staplers and green staplers for sale. He sold 180 black staplers. 60% of the staplers sold were green.

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

	Black	Green	Total	Total in percent
Before	5.75 u	4.25 u	10 u	100%
Change	- 40% - 2 u	- 60% - 3 u	- 100% - 5 u	- 50%
After	75% 3.75 u	25% 1.25 u	100% 5 u	50%

60% = ⁶⁰₁₀₀ = ³₅

Total number of staplers sold = 5 u
Number of green staplers sold = 3 u

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

2 u = 180

1 u = 180 ÷ 2 = 90

Total number of staplers sold
= 5 u
= 5 x 90
= 450

(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 black = 75%
Percent of the staplers left unsold that were green = 100% - 75% = 25%

Number of the staplers left unsold that were green
= 25% x 5 u
= ²⁵₁₀₀ x 5 u
= 1.25 u

Number of green staplers that Luke had at first
= 1.25 u + 3 u
= 4.25 u
= 4.25 x 90
= 382.5

Answer(s): (a) 450; (b) 382.5