The ratio of the number of red coins to green coins is 9 : 7. After Eric gives away 50 red coins and buys another 90 green coins, there is equal number of red coins and green coins. How many coins does Eric have now?
| |
Red |
Green |
| Before |
9 u |
7 u |
| Change |
- 50 |
+ 90 |
| After |
9 u - 50 |
7 u + 90 |
The number of red coins and green coins in the end is the same.
9 u - 50 = 7 u + 90
9 u - 7 u = 90 + 50
2 u = 140
1 u = 140 ÷ 2 = 70
Number of coins that Eric has now
= 9 u - 50 + 7 u + 90
= 9 u + 7 u - 50 + 90
= 16 u + 40
= 16 x 70 + 40
= 1120 + 40
= 1160
Answer(s): 1160
