The ratio of the number of red stamps to green stamps is 9 : 4. After Ivan gives away 40 red stamps and buys another 70 green stamps, there is equal number of red stamps and green stamps. How many stamps does Ivan have now?
| |
Red |
Green |
| Before |
9 u |
4 u |
| Change |
- 40 |
+ 70 |
| After |
9 u - 40 |
4 u + 70 |
The number of red stamps and green stamps in the end is the same.
9 u - 40 = 4 u + 70
9 u - 4 u = 70 + 40
5 u = 110
1 u = 110 ÷ 5 = 22
Number of stamps that Ivan has now
= 9 u - 40 + 4 u + 70
= 9 u + 4 u - 40 + 70
= 13 u + 30
= 13 x 22 + 30
= 286 + 30
= 316
Answer(s): 316
