Mrs Ong had a total of 84 yellow and pink tulips in the ratio of 9 : 5. After she had given away 4 times as many yellow tulips as pink tulips, the number of yellow and pink tulips left was in the ratio of 5 : 4. How many more yellow tulips than pink tulips did she give away?

	Yellow	Pink	Total
Before	9 b	5 b	14 b
Change	- 4 u	- 1 u
After	5 p	4 p

	Make p the same (1)x4 = (3)	Yellow (1)	Pink (2)	Make p the same (2)x5 = (4)
Before	216	54	30	150
Change	- 16 u	- 4 u	- 1 u	- 5 u
After	20 p	5 p	4 p	20 p

Number of tulips at first
= 9 b + 5 b
= 14 b

14 b = 84

1 b = 84 ÷ 14 = 6

Number of yellow tulips at first
= 9 b
= 9 x 6
= 54

Number of pink tulips at first
= 5 b
= 5 x 6
= 30

54 - 4 u = 5 p --- (1)

30 - 1 u = 4 p --- (2)

Make p the same.

(1)_x4 
216 - 16 u = 20 p --- (3)

(2)_x5 = (4)
150 - 5 u = 20 p --- (4)

(3) = (4)
216 - 16 u = 150 - 5 u
16 u - 5 u = 216 - 150
11 u = 66

1 u = 66 ÷ 11 = 6

Number of more yellow tulips than pink tulips that she gave away
= 4 u - 1 u
= 3 u
= 3 x 6
= 18

Answer(s): 18