PSLE
Archie had pink staplers and black staplers for sale. He sold 700 pink staplers. 30% of the staplers sold were black.

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

	Pink	Black	Total	Total in percent
Before	13 u	7 u	20 u	100%
Change	- 70% - 7 u	- 30% - 3 u	- 100% - 10 u	- 50%
After	60% 6 u	40% 4 u	100% 10 u	50%

30% = ³⁰₁₀₀ = ³₁₀

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

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

7 u = 700

1 u = 700 ÷ 7 = 100

Total number of staplers sold
= 10 u
= 10 x 100
= 1000

(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 pink = 60%
Percent of the staplers left unsold that were black = 100% - 60% = 40%

Number of the staplers left unsold that were black
= 40% x 10 u
= ⁴⁰₁₀₀ x 10 u
= 4 u

Number of black staplers that Archie had at first
= 4 u + 3 u
= 7 u
= 7 x 100
= 700

Answer(s): (a) 1000; (b) 700