PSLE
Asher had gold notebooks and blue notebooks for sale. He sold 120 gold notebooks. 70% of the notebooks sold were blue.

1. How many gold notebooks and blue notebooks did Asher sell altogether?
2. He sold 50% of his notebooks. 80% of the notebooks left unsold were gold. How many blue notebooks did Asher have at first?

	Gold	Blue	Total	Total in percent
Before	11 u	9 u	20 u	100%
Change	- 30% - 3 u	- 70% - 7 u	- 100% - 10 u	- 50%
After	80% 8 u	20% 2 u	100% 10 u	50%

70% = ⁷⁰₁₀₀ = ⁷₁₀

Total number of notebooks sold = 10 u
Number of blue notebooks sold = 7 u

Number of gold notebooks sold
= 10 u - 7 u
= 3 u

3 u = 120

1 u = 120 ÷ 3 = 40

Total number of notebooks sold
= 10 u
= 10 x 40
= 400

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

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

Percent of the notebooks left unsold that were gold = 80%
Percent of the notebooks left unsold that were blue = 100% - 80% = 20%

Number of the notebooks left unsold that were blue
= 20% x 10 u
= ²⁰₁₀₀ x 10 u
= 2 u

Number of blue notebooks that Asher had at first
= 2 u + 7 u
= 9 u
= 9 x 40
= 360

Answer(s): (a) 400; (b) 360