The ratio of the number of red coins to green coins is 7 : 5. After Lee gives away 10 red coins and buys another 60 green coins, there is equal number of red coins and green coins. How many coins does Lee have now?
| |
Red |
Green |
| Before |
7 u |
5 u |
| Change |
- 10 |
+ 60 |
| After |
7 u - 10 |
5 u + 60 |
The number of red coins and green coins in the end is the same.
7 u - 10 = 5 u + 60
7 u - 5 u = 60 + 10
2 u = 70
1 u = 70 ÷ 2 = 35
Number of coins that Lee has now
= 7 u - 10 + 5 u + 60
= 7 u + 5 u - 10 + 60
= 12 u + 50
= 12 x 35 + 50
= 420 + 50
= 470
Answer(s): 470
