PSLE
Albert had gold notebooks and pink notebooks for sale. He sold 360 gold notebooks. 40% of the notebooks sold were pink.

1. How many gold notebooks and pink notebooks did Albert sell altogether?
2. He sold 50% of his notebooks. 70% of the notebooks left unsold were gold. How many pink notebooks did Albert have at first?

	Gold	Pink	Total	Total in percent
Before	6.5 u	3.5 u	10 u	100%
Change	- 60% - 3 u	- 40% - 2 u	- 100% - 5 u	- 50%
After	70% 3.5 u	30% 1.5 u	100% 5 u	50%

40% = ⁴⁰₁₀₀ = ²₅

Total number of notebooks sold = 5 u
Number of pink notebooks sold = 2 u

Number of gold notebooks sold
= 5 u - 2 u
= 3 u

3 u = 360

1 u = 360 ÷ 3 = 120

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

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

50% of the notebooks that were sold = 5 u
50% of the notebooks that were left unsold = 5 u

Percent of the notebooks left unsold that were gold = 70%
Percent of the notebooks left unsold that were pink = 100% - 70% = 30%

Number of the notebooks left unsold that were pink
= 30% x 5 u
= ³⁰₁₀₀ x 5 u
= 1.5 u

Number of pink notebooks that Albert had at first
= 1.5 u + 2 u
= 3.5 u
= 3.5 x 120
= 420

Answer(s): (a) 600; (b) 420