Ethan and Bobby had 54 files. After Ethan gave 15 files to Bobby. Bobby, in return, gave half of his files to Ethan. In the end, Ethan had twice as many files as Bobby. How many files did Ethan have at first?
| |
Ethan |
Bobby |
Total |
| Before |
1 u + 15 |
2 u - 15 |
54 |
| Change 1 |
- 15 |
+ 15 |
|
| After 1 |
1 u |
2 u |
|
| Change 2 |
+ 1 u |
- 1 u |
|
| After 2 |
2 u |
1 u |
54 |
Total number of files that Ethan and Bobby had at first and in the end remains unchanged.
Total number of files
= 2 u + 1 u
= 3 u
1 u = 54 ÷ 3 = 18
Number of files that Ethan had at first
= 1 u + 15
= 18 + 15
= 33
Answer(s): 33
