Michael had 6 times as many erasers as Tommy at first. Then each of them bought an equal number of new erasers. In the end, Tommy had 15 erasers and Michael had 3 times as many erasers as Tommy. How many erasers did both of them buy altogether?
| |
Michael |
Tommy |
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 Tommy had in the end = 5 u
5 u = 15
1 u = 15 ÷ 5 = 3
Number of erasers that Michael 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
