PSLE
Riordan had silver staplers and orange staplers for sale. He sold 490 silver staplers. 30% of the staplers sold were orange.

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

	Silver	Orange	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 orange staplers sold = 3 u

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

7 u = 490

1 u = 490 ÷ 7 = 70

Total number of staplers sold
= 10 u
= 10 x 70
= 700

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

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

Number of orange staplers that Riordan had at first
= 4 u + 3 u
= 7 u
= 7 x 70
= 490

Answer(s): (a) 700; (b) 490