PSLE
Japheth had blue notebooks and pink notebooks for sale. He sold 700 blue notebooks. 30% of the notebooks sold were pink.

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

	Blue	Pink	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 pink notebooks sold = 3 u

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

7 u = 700

1 u = 700 ÷ 7 = 100

Total number of notebooks sold
= 10 u
= 10 x 100
= 1000

(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 pink = 100% - 60% = 40%

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

Number of pink notebooks that Japheth had at first
= 4 u + 3 u
= 7 u
= 7 x 100
= 700

Answer(s): (a) 1000; (b) 700