The ratio of the number of red coins to blue coins is 9 : 7. After Archie gives away 60 red coins and buys another 90 blue coins, there is equal number of red coins and blue coins. How many coins does Archie have now?
| |
Red |
Blue |
| Before |
9 u |
7 u |
| Change |
- 60 |
+ 90 |
| After |
9 u - 60 |
7 u + 90 |
The number of red coins and blue coins in the end is the same.
9 u - 60 = 7 u + 90
9 u - 7 u = 90 + 60
2 u = 150
1 u = 150 ÷ 2 = 75
Number of coins that Archie has now
= 9 u - 60 + 7 u + 90
= 9 u + 7 u - 60 + 90
= 16 u + 30
= 16 x 75 + 30
= 1200 + 30
= 1230
Answer(s): 1230
