Daniel, Albert and Eric had some stickers in the ratio of 4 : 5 : 9. Eric gave 50% of his stickers to Daniel and Albert. As a result, Daniel had the same number of stickers as Albert and Eric had 36 fewer stickers than Daniel.

1. What was the percentage increase in Daniel's stickers after receiving from Eric?
2. How many stickers did Albert have at first?

Daniel	Albert	Eric	Total
4 u	5 u	9 u	18 u
+ 4.5 u		- 4.5 u
6.75 u	6.75 u	4.5 u	18 u

(a)
Number of stickers that Eric gave away
= 50% x 9
= ⁵⁰₁₀₀ x 9
= 4.5 u

Number of stickers that Daniel and Albert each had in the end
= (18 u - 4.5 u) ÷ 2
= 13.5 u ÷ 2
= 6.75 u

Increase in the number of stickers that Daniel had
= 6.75 u - 4 u
= 2.75 u

Percentage increase in Daniel's stickers after receiving from Eric
= ^2.75₄ x 100%
= 68.75%

(b)
6.75 u = 4.5 u + 36
6.75 u - 4.5 u = 36
2.25 u = 36

1 u = 36 ÷ 2.25 = 16

Number of stickers that Albert had at first
= 5 u
= 5 x 16
= 80

Answer(s): (a) 68.75%; (b) 80