Ethan, Ben and Harry had the same number of marbles. Harry gave 0.6 of his marbles to Ben. Then Ben gave 0.25 of his marbles to Ethan. Finally, after Ben gave 30 marbles to Harry, he had the same number of marbles as Harry. How many marbles did Harry have at first?
| |
Ethan |
Ben |
Harry |
| Before |
1 u |
1 u |
1 u |
| Change 1 |
|
+ 0.6 u |
- 0.6 u |
| After 1 |
1 u |
1.6 u |
0.4 u |
| Change 2 |
+ 0.4 u |
- 0.4 u |
|
| After 2 |
1.4 u |
1.2 u |
0.4 u |
| Change 3 |
|
- 30 |
+ 30 |
| After 3 |
1.4 u |
1.2 u - 30 |
0.4 u + 30 |
Number of marbles that Ben gave to Ethan
= 0.25 x 1.6 u
= 0.4 u
The number of marbles that Ben and Harry had in the end is the same.
1.2 u - 30 = 0.4 u + 30
1.2 u - 0.4 u = 30 + 30
0.8 u = 60
1 u = 60 ÷ 0.8 = 75
Number of marbles that Harry had at first
= 1 u
= 75
Answer(s): 75
