Cindy and Risa had an equal number of erasers at first. Cindy used
14 of her erasers and Risa used
17 of her erasers. They used 99 erasers altogether. How many erasers did Risa have in the end?
|
Cindy |
Risa |
Before |
4x7 = 28 u |
7x4 = 28 u |
Change |
- 1x7 = - 7 u |
- 1x4 = - 4 u |
After |
3x7 = 21 u |
6x4 = 24 u |
The number of erasers that Cindy and Risa each had at first is the same. Make the number of erasers that Cindy and Risa each had at first the same. LCM of 4 and 7 is 28.
Number of erasers that Cindy and Risa used
= 7 u + 4 u
= 11 u
11 u = 99
1 u = 99 ÷ 11 = 9
Number of erasers that Risa had in the end
= 24 u
= 24 x 9
= 216
Answer(s): 216