The ratio of the number of blue stickers to red stickers is 7 : 3.
After Adam buys another 15 red stickers and gives away 13 blue stickers,
the ratio becomes of the number of blue stickers to red stickers is 4 : 3.
How many stickers does Adam have now?
|
Make p the same (1) x 3 = (3) |
(1) Blue |
(2) Red |
Make p the same (2) x 4 = (4) |
Before |
21 u |
7 u |
3 u |
12 u |
Change |
- 39 |
- 13 |
+ 15 |
+ 60 |
After |
12 p |
4 p |
3 p |
12 p |
7 u + 15 = 4 p --- (1)
3 u - 13 = 3 p --- (2)
Make p the same.
(1)
x 321 u - 39 = 12 p --- (3)
(2)
x 412 u + 60 = 12 p --- (4)
(3) = (4)
21 u - 39 = 12 u + 60
21 u - 12 u = 39 + 60
9 u = 99
1 u = 99 ÷ 9 = 11
Number of stickers that Adam have now
= 7 u + 15 + 3 u - 13
= 7 u + 3 u + 15 - 13
= 10 u + 2
= 10 x 11 + 2
= 110 + 2
= 112
Answer(s): 112