Bobby had 6 times as many erasers as Will at first. Then each of them bought an equal number of new erasers. In the end, Will had 20 erasers and Bobby had 4 times as many erasers as Will. How many erasers did both of them buy altogether?
| |
Bobby |
Will |
Difference |
| Before |
6x3 =
18 u |
1x3 =
3 u |
5x3 =
15 u |
| Change |
+ ? |
+ ? |
|
| After |
4x5 =
20 u |
1x5 =
5 u |
3x5 =
15 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 3 is 15.
Number of erasers that Will had in the end = 5 u
5 u = 20
1 u = 20 ÷ 5 = 4
Number of erasers that Bobby bought
= 20 u - 18 u
= 2 u
Number of erasers that both of them bought altogether
= 2 x 2 u
= 4 u
= 4 x 4
= 16
Answer(s): 16
