PSLE
Paul had orange staplers and black staplers for sale. He sold 200 orange staplers. 60% of the staplers sold were black.

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

	Orange	Black	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 black staplers sold = 3 u

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

2 u = 200

1 u = 200 ÷ 2 = 100

Total number of staplers sold
= 5 u
= 5 x 100
= 500

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

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

Number of black staplers that Paul had at first
= 1.25 u + 3 u
= 4.25 u
= 4.25 x 100
= 425

Answer(s): (a) 500; (b) 425