The ratio of the number of green marbles to red marbles is 7 : 2. After Elijah gives away 10 green marbles and buys another 80 red marbles, there is equal number of green marbles and red marbles. How many marbles does Elijah have now?
| |
Green |
Red |
| Before |
7 u |
2 u |
| Change |
- 10 |
+ 80 |
| After |
7 u - 10 |
2 u + 80 |
The number of green marbles and red marbles in the end is the same.
7 u - 10 = 2 u + 80
7 u - 2 u = 80 + 10
5 u = 90
1 u = 90 ÷ 5 = 18
Number of marbles that Elijah has now
= 7 u - 10 + 2 u + 80
= 7 u + 2 u - 10 + 80
= 9 u + 70
= 9 x 18 + 70
= 162 + 70
= 232
Answer(s): 232
