PSLE
Tim had blue staplers and silver staplers for sale. He sold 240 blue staplers. 60% of the staplers sold were silver.

1. How many blue staplers and silver staplers did Tim sell altogether?
2. He sold 50% of his staplers. 70% of the staplers left unsold were blue. How many silver staplers did Tim have at first?

	Blue	Silver	Total	Total in percent
Before	5.5 u	4.5 u	10 u	100%
Change	- 40% - 2 u	- 60% - 3 u	- 100% - 5 u	- 50%
After	70% 3.5 u	30% 1.5 u	100% 5 u	50%

60% = ⁶⁰₁₀₀ = ³₅

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

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

2 u = 240

1 u = 240 ÷ 2 = 120

Total number of staplers sold
= 5 u
= 5 x 120
= 600

(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 blue = 70%
Percent of the staplers left unsold that were silver = 100% - 70% = 30%

Number of the staplers left unsold that were silver
= 30% x 5 u
= ³⁰₁₀₀ x 5 u
= 1.5 u

Number of silver staplers that Tim had at first
= 1.5 u + 3 u
= 4.5 u
= 4.5 x 120
= 540

Answer(s): (a) 600; (b) 540