Peter had 5 times as many erasers as Andy at first. Then each of them bought an equal number of new erasers. In the end, Andy had 12 erasers and Peter had 4 times as many erasers as Andy. How many erasers did both of them buy altogether?
| |
Peter |
Andy |
Difference |
| Before |
5x3 =
15 u |
1x3 =
3 u |
4x3 =
12 u |
| Change |
+ ? |
+ ? |
|
| After |
4x4 =
16 u |
1x4 =
4 u |
3x4 =
12 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 4 and 3 is 12.
Number of erasers that Andy had in the end = 4 u
4 u = 12
1 u = 12 ÷ 4 = 3
Number of erasers that Peter bought
= 16 u - 15 u
= 1 u
Number of erasers that both of them bought altogether
= 2 x 1 u
= 2 u
= 2 x 3
= 6
Answer(s): 6
