Bryan, Ethan and Oliver had 128 marbles. After Bryan used 21 marbles and Ethan used
38 of her marbles, Bryan had thrice as many marbles left as Ethan. Oliver bought another 25 marbles, he had twice the number of marbles Ethan had left. How many marbles did Oliver have at first?
| |
Bryan |
Ethan |
Oliver |
Total |
| Before |
15 u + 21 |
8 u |
10 u - 25 |
128 |
| Change |
- 21 |
- 3 u |
+ 25 |
|
| After |
15 u |
5 u |
10 u |
|
Comparing Bryan
and Ethan in the end |
3 |
1 |
|
|
Comparing Oliver
and Ethan in the end |
|
1 |
2 |
|
Number of marbles that Bryan had in the end
= 3 x 5 u
= 15 u
Number of marbles that Oliver had in the end
= 2 x 5 u
= 10 u
Total number of marbles at first
= 15 u + 21 + 8 u + 10 u - 25
= 33 u - 4
33 u - 4 = 128
33 u = 128 + 4
33 u = 132
1 u = 132 ÷ 33 = 4
Number of marbles that Oliver had at first
= 10 u - 25
= 10 x 4 - 25
= 40 - 25
= 15
Answer(s): 15
