Esther had 21 more erasers than Vanessa. After Vanessa gave away
15 of her erasers, Esther had thrice as many erasers as Vanessa. How many erasers did Vanessa have at first?
| |
Esther |
Vanessa |
Comparing Esther and
Vanessa at first |
21 more |
|
| Before |
12 u |
5 u |
| Change |
|
- 1 u |
| After |
12 u |
4 u |
Comparing Esther and
Vanessa in the end |
3x4 =
12 u |
1x4 =
4 u |
Number of erasers that Vanessa had in the end is repeated. Make the number of erasers that Vanessa had in the end the same. LCM of 1 and 4 is 4.
Number of erasers that Esther had at first = 12 u
Number of erasers that Esther had more than Vanessa at first
= 12 u - 5 u
= 7 u
7 u = 21
1 u = 21 ÷ 7 = 3
Number of erasers that Vanessa had at first
= 5 u
= 5 x 3
= 15
Answer(s): 15
