Zoe and Tammy have some pencils in the ratio 5 : 13. Zoe has 40 less pencils than Tammy. How many pencils must Tammy give to Zoe so that they will have the same number of pencils?
| |
Zoe |
Tammy |
Total |
| Before |
5 u |
13 u |
18 u |
| Change |
+ 4 u |
- 4 u |
|
After |
1x9 =
9 u |
1x9 =
9 u |
2x9 =
18 u |
The total number of pencils remains unchanged. Make the total number of pencils at first and in the end the same. LCM of 2 and 18 is 18.
Difference in the number of pencils at first
= 13 u - 5 u
= 8 u
8 u = 40
1 u = 40 ÷ 8 = 5
Number of pencils that each of them had in the end
= 18 u ÷ 2
= 9 u
Number of pencils that Tammy must give to Zoe
= 9 u - 5 u
= 4 u
= 4 x 5
= 20
Answer(s): 20
