The ratio of the number of red coins to blue coins is 3 : 1. After Andy gives away 20 red coins and buys another 50 blue coins, there is equal number of red coins and blue coins. How many coins does Andy have now?
| |
Red |
Blue |
| Before |
3 u |
1 u |
| Change |
- 20 |
+ 50 |
| After |
3 u - 20 |
1 u + 50 |
The number of red coins and blue coins in the end is the same.
3 u - 20 = 1 u + 50
3 u - 1 u = 50 + 20
2 u = 70
1 u = 70 ÷ 2 = 35
Number of coins that Andy has now
= 3 u - 20 + 1 u + 50
= 3 u + 1 u - 20 + 50
= 4 u + 30
= 4 x 35 + 30
= 140 + 30
= 170
Answer(s): 170
