Betty had 99 more erasers than Zoe. After Zoe gave away
37 of her erasers, Betty had four times as many erasers as Zoe. How many erasers did Zoe have at first?
| |
Betty |
Zoe |
Comparing Betty and
Zoe at first |
99 more |
|
| Before |
16 u |
7 u |
| Change |
|
- 3 u |
| After |
16 u |
4 u |
Comparing Betty and
Zoe in the end |
4x4 =
16 u |
1x4 =
4 u |
Number of erasers that Zoe had in the end is repeated. Make the number of erasers that Zoe had in the end the same. LCM of 1 and 4 is 4.
Number of erasers that Betty had at first = 16 u
Number of erasers that Betty had more than Zoe at first
= 16 u - 7 u
= 9 u
9 u = 99
1 u = 99 ÷ 9 = 11
Number of erasers that Zoe had at first
= 7 u
= 7 x 11
= 77
Answer(s): 77
