PSLE
Vaidev had purple notebooks and blue notebooks for sale. He sold 210 purple notebooks. 30% of the notebooks sold were blue.

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

	Purple	Blue	Total	Total in percent
Before	14 u	6 u	20 u	100%
Change	- 70% - 7 u	- 30% - 3 u	- 100% - 10 u	- 50%
After	70% 7 u	30% 3 u	100% 10 u	50%

30% = ³⁰₁₀₀ = ³₁₀

Total number of notebooks sold = 10 u
Number of blue notebooks sold = 3 u

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

7 u = 210

1 u = 210 ÷ 7 = 30

Total number of notebooks sold
= 10 u
= 10 x 30
= 300

(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 purple = 70%
Percent of the notebooks left unsold that were blue = 100% - 70% = 30%

Number of the notebooks left unsold that were blue
= 30% x 10 u
= ³⁰₁₀₀ x 10 u
= 3 u

Number of blue notebooks that Vaidev had at first
= 3 u + 3 u
= 6 u
= 6 x 30
= 180

Answer(s): (a) 300; (b) 180