PSLE
Gabriel had black markers and purple markers for sale. He sold 180 black markers. 70% of the markers sold were purple.

1. How many black markers and purple markers did Gabriel sell altogether?
2. He sold 50% of his markers. 70% of the markers left unsold were black. How many purple markers did Gabriel have at first?

	Black	Purple	Total	Total in percent
Before	10 u	10 u	20 u	100%
Change	- 30% - 3 u	- 70% - 7 u	- 100% - 10 u	- 50%
After	70% 7 u	30% 3 u	100% 10 u	50%

70% = ⁷⁰₁₀₀ = ⁷₁₀

Total number of markers sold = 10 u
Number of purple markers sold = 7 u

Number of black markers sold
= 10 u - 7 u
= 3 u

3 u = 180

1 u = 180 ÷ 3 = 60

Total number of markers sold
= 10 u
= 10 x 60
= 600

(b)
Percent of the markers left unsold
= 100% - 50%
= 50%

50% of the markers that were sold = 10 u
50% of the markers that were left unsold = 10 u

Percent of the markers left unsold that were black = 70%
Percent of the markers left unsold that were purple = 100% - 70% = 30%

Number of the markers left unsold that were purple
= 30% x 10 u
= ³⁰₁₀₀ x 10 u
= 3 u

Number of purple markers that Gabriel had at first
= 3 u + 7 u
= 10 u
= 10 x 60
= 600

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