PSLE
Sam had orange staplers and yellow staplers for sale. He sold 180 orange staplers. 40% of the staplers sold were yellow.

1. How many orange staplers and yellow staplers did Sam sell altogether?
2. He sold 50% of his staplers. 80% of the staplers left unsold were orange. How many yellow staplers did Sam have at first?

	Orange	Yellow	Total	Total in percent
Before	7 u	3 u	10 u	100%
Change	- 60% - 3 u	- 40% - 2 u	- 100% - 5 u	- 50%
After	80% 4 u	20% 1 u	100% 5 u	50%

40% = ⁴⁰₁₀₀ = ²₅

Total number of staplers sold = 5 u
Number of yellow staplers sold = 2 u

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

3 u = 180

1 u = 180 ÷ 3 = 60

Total number of staplers sold
= 5 u
= 5 x 60
= 300

(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 = 80%
Percent of the staplers left unsold that were yellow = 100% - 80% = 20%

Number of the staplers left unsold that were yellow
= 20% x 5 u
= ²⁰₁₀₀ x 5 u
= 1 u

Number of yellow staplers that Sam had at first
= 1 u + 2 u
= 3 u
= 3 x 60
= 180

Answer(s): (a) 300; (b) 180