Oliver had 4 times as many erasers as Ryan at first. Then each of them bought an equal number of new erasers. In the end, Ryan had 30 erasers and Oliver had 3 times as many erasers as Ryan. How many erasers did both of them buy altogether?
| |
Oliver |
Ryan |
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 Ryan had in the end = 3 u
3 u = 30
1 u = 30 ÷ 3 = 10
Number of erasers that Oliver bought
= 9 u - 8 u
= 1 u
Number of erasers that both of them bought altogether
= 2 x 1 u
= 2 u
= 2 x 10
= 20
Answer(s): 20
