Mrs Lim had a total of 55 pink and white lilies in the ratio of 7 : 4. After she had given away 3 times as many pink lilies as white lilies, the number of pink and white lilies left was in the ratio of 4 : 3. How many more pink lilies than white lilies did she give away?

	Pink	White	Total
Before	7 b	4 b	11 b
Change	- 3 u	- 1 u
After	4 p	3 p

	Make p the same (1)x3 = (3)	Pink (1)	White (2)	Make p the same (2)x4 = (4)
Before	105	35	20	80
Change	- 9 u	- 3 u	- 1 u	- 4 u
After	12 p	4 p	3 p	12 p

Number of lilies at first
= 7 b + 4 b
= 11 b

11 b = 55

1 b = 55 ÷ 11 = 5

Number of pink lilies at first
= 7 b
= 7 x 5
= 35

Number of white lilies at first
= 4 b
= 4 x 5
= 20

35 - 3 u = 4 p --- (1)

20 - 1 u = 3 p --- (2)

Make p the same.

(1)_x3 
105 - 9 u = 12 p --- (3)

(2)_x4 = (4)
80 - 4 u = 12 p --- (4)

(3) = (4)
105 - 9 u = 80 - 4 u
9 u - 4 u = 105 - 80
5 u = 25

1 u = 25 ÷ 5 = 5

Number of more pink lilies than white lilies that she gave away
= 3 u - 1 u
= 2 u
= 2 x 5
= 10

Answer(s): 10