Mrs Zhang had a total of 90 white and pink daisies in the ratio of 7 : 3. After she had given away 6 times as many white daisies as pink daisies, the number of white and pink daisies left was in the ratio of 3 : 2. How many more white daisies than pink daisies did she give away?

	White	Pink	Total
Before	7 b	3 b	10 b
Change	- 6 u	- 1 u
After	3 p	2 p

	Make p the same (1)x2 = (3)	White (1)	Pink (2)	Make p the same (2)x3 = (4)
Before	126	63	27	81
Change	- 12 u	- 6 u	- 1 u	- 3 u
After	6 p	3 p	2 p	6 p

Number of daisies at first
= 7 b + 3 b
= 10 b

10 b = 90

1 b = 90 ÷ 10 = 9

Number of white daisies at first
= 7 b
= 7 x 9
= 63

Number of pink daisies at first
= 3 b
= 3 x 9
= 27

63 - 6 u = 3 p --- (1)

27 - 1 u = 2 p --- (2)

Make p the same.

(1)_x2 
126 - 12 u = 6 p --- (3)

(2)_x3 = (4)
81 - 3 u = 6 p --- (4)

(3) = (4)
126 - 12 u = 81 - 3 u
12 u - 3 u = 126 - 81
9 u = 45

1 u = 45 ÷ 9 = 5

Number of more white daisies than pink daisies that she gave away
= 6 u - 1 u
= 5 u
= 5 x 5
= 25

Answer(s): 25