PSLE
Rael had blue notebooks and gold notebooks for sale. He sold 560 blue notebooks. 30% of the notebooks sold were gold.

1. How many blue notebooks and gold notebooks did Rael sell altogether?
2. He sold 50% of his notebooks. 60% of the notebooks left unsold were blue. How many gold notebooks did Rael have at first?

	Blue	Gold	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 notebooks sold = 10 u
Number of gold notebooks sold = 3 u

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

7 u = 560

1 u = 560 ÷ 7 = 80

Total number of notebooks sold
= 10 u
= 10 x 80
= 800

(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 blue = 60%
Percent of the notebooks left unsold that were gold = 100% - 60% = 40%

Number of the notebooks left unsold that were gold
= 40% x 10 u
= ⁴⁰₁₀₀ x 10 u
= 4 u

Number of gold notebooks that Rael had at first
= 4 u + 3 u
= 7 u
= 7 x 80
= 560

Answer(s): (a) 800; (b) 560