Peter had 4 times as many erasers as Ben at first. Then each of them bought an equal number of new erasers. In the end, Ben had 18 erasers and Peter had 3 times as many erasers as Ben. How many erasers did both of them buy altogether?
| |
Peter |
Ben |
Difference |
| Before |
4x2 =
8 u |
1x2 =
2 u |
3x2 =
6 u |
| Change |
+ ? |
+ ? |
|
| After |
3x3 =
9 u |
1x3 =
3 u |
2x3 =
6 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 3 and 2 is 6.
Number of erasers that Ben had in the end = 3 u
3 u = 18
1 u = 18 ÷ 3 = 6
Number of erasers that Peter bought
= 9 u - 8 u
= 1 u
Number of erasers that both of them bought altogether
= 2 x 1 u
= 2 u
= 2 x 6
= 12
Answer(s): 12
