PSLE
Jenson had yellow notebooks and blue notebooks for sale. He sold 360 yellow notebooks. 40% of the notebooks sold were blue.

1. How many yellow notebooks and blue notebooks did Jenson sell altogether?
2. He sold 50% of his notebooks. 75% of the notebooks left unsold were yellow. How many blue notebooks did Jenson have at first?

	Yellow	Blue	Total	Total in percent
Before	6.75 u	3.25 u	10 u	100%
Change	- 60% - 3 u	- 40% - 2 u	- 100% - 5 u	- 50%
After	75% 3.75 u	25% 1.25 u	100% 5 u	50%

40% = ⁴⁰₁₀₀ = ²₅

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

Number of yellow 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 yellow = 75%
Percent of the notebooks left unsold that were blue = 100% - 75% = 25%

Number of the notebooks left unsold that were blue
= 25% x 5 u
= ²⁵₁₀₀ x 5 u
= 1.25 u

Number of blue notebooks that Jenson had at first
= 1.25 u + 2 u
= 3.25 u
= 3.25 x 120
= 390

Answer(s): (a) 600; (b) 390