The ratio of the number of blue coins to red coins is 7 : 5. After Elijah gives away 70 blue coins and buys another 80 red coins, there is equal number of blue coins and red coins. How many coins does Elijah have now?
| |
Blue |
Red |
| Before |
7 u |
5 u |
| Change |
- 70 |
+ 80 |
| After |
7 u - 70 |
5 u + 80 |
The number of blue coins and red coins in the end is the same.
7 u - 70 = 5 u + 80
7 u - 5 u = 80 + 70
2 u = 150
1 u = 150 ÷ 2 = 75
Number of coins that Elijah has now
= 7 u - 70 + 5 u + 80
= 7 u + 5 u - 70 + 80
= 12 u + 10
= 12 x 75 + 10
= 900 + 10
= 910
Answer(s): 910
