Oliver had 6 times as many erasers as John at first. Then each of them bought an equal number of new erasers. In the end, John had 15 erasers and Oliver had 3 times as many erasers as John. How many erasers did both of them buy altogether?
| |
Oliver |
John |
Difference |
| Before |
6x2 =
12 u |
1x2 =
2 u |
5x2 =
10 u |
| Change |
+ ? |
+ ? |
|
| After |
3x5 =
15 u |
1x5 =
5 u |
2x5 =
10 u |
The difference in the number of erasers at first and in the end remains unchanged. Make the difference in the number of erasers at first and in the end the same. LCM of 5 and 2 is 10.
Number of erasers that John had in the end = 5 u
5 u = 15
1 u = 15 ÷ 5 = 3
Number of erasers that Oliver bought
= 15 u - 12 u
= 3 u
Number of erasers that both of them bought altogether
= 2 x 3 u
= 6 u
= 6 x 3
= 18
Answer(s): 18
