Fanny and Betty have some notebooks in the ratio 3 : 7. Fanny has 80 less notebooks than Betty. How many notebooks must Betty give to Fanny so that they will have the same number of notebooks?
| |
Fanny |
Betty |
Total |
| Before |
3 u |
7 u |
10 u |
| Change |
+ 2 u |
- 2 u |
|
After |
1x5 =
5 u |
1x5 =
5 u |
2x5 =
10 u |
The total number of notebooks remains unchanged. Make the total number of notebooks at first and in the end the same. LCM of 2 and 10 is 10.
Difference in the number of notebooks at first
= 7 u - 3 u
= 4 u
4 u = 80
1 u = 80 ÷ 4 = 20
Number of notebooks that each of them had in the end
= 10 u ÷ 2
= 5 u
Number of notebooks that Betty must give to Fanny
= 5 u - 3 u
= 2 u
= 2 x 20
= 40
Answer(s): 40
