The ratio of the number of red stickers to blue stickers is 8 : 3.
After Adam buys another 21 blue stickers and gives away 16 red stickers,
the ratio becomes of the number of red stickers to blue stickers is 7 : 3.
How many stickers does Adam have now?
|
Make p the same (1) x 3 = (3) |
(1) Red |
(2) Blue |
Make p the same (2) x 7 = (4) |
Before |
24 u |
8 u |
3 u |
21 u |
Change |
- 48 |
- 16 |
+ 21 |
+ 147 |
After |
21 p |
7 p |
3 p |
21 p |
8 u + 21 = 7 p --- (1)
3 u - 16 = 3 p --- (2)
Make p the same.
(1)
x 324 u - 48 = 21 p --- (3)
(2)
x 721 u + 147 = 21 p --- (4)
(3) = (4)
24 u - 48 = 21 u + 147
24 u - 21 u = 48 + 147
3 u = 195
1 u = 195 ÷ 3 = 65
Number of stickers that Adam have now
= 8 u + 21 + 3 u - 16
= 8 u + 3 u + 21 - 16
= 11 u + 5
= 11 x 65 + 5
= 715 + 5
= 720
Answer(s): 720