The ratio of the number of red stickers to green stickers is 7 : 3.
After Adam gives away 81 red stickers and gives away 90 green stickers,
the ratio becomes of the number of red stickers to green stickers is 8 : 3.
How many stickers does Adam have now?
|
Make p the same (1) x 3 = (3) |
(1) Red |
(2) Green |
Make p the same (2) x 8 = (4) |
Before |
21 u |
7 u |
3 u |
24 u |
Change |
- 243 |
- 81 |
- 90 |
- 720 |
After |
24 p |
8 p |
3 p |
24 p |
7 u - 81 = 8 p --- (1)
3 u - 90 = 3 p --- (2)
Make p the same.
(1) x 3
21 u - 243 = 24 p --- (3)
(2) x 8
24 u - 720 = 24 p --- (4)
(4) = (3)
24 u - 720 = 21 u - 243
24 u - 21 u = 720 - 243
3 u = 477
1 u = 477 ÷ 3 = 159
Number of stickers that Adam has now
= 7 u - 81 + 3 u - 90
= 10 u - 171
= 10 x 159 - 171
= 1590 - 171
= 1419
Answer(s): 1419