Risa and Opal collected erasers. Risa gave 40% of her erasers to Opal. As a result, Opal's erasers increased by 80%. If Risa had 12 erasers left, find the total number of erasers the two girls had at first.
| |
Risa |
Opal |
Comparing the change
in Opal's erasers |
| Before |
5x2 =
10 u |
|
5x1 =
5 u |
| Change |
- 2x2 =
- 4 u |
+ 2x2 =
+ 4 u |
+ 4x1 =
+ 4 u |
| After |
3x2 =
6 u |
|
9x1 =
9 u |
40% =
40100 =
25 80% =
80100 =
45 The number of erasers that Risa gave to Opal is repeated. Make the number of erasers that Risa gave to Opal the same. LCM of 2 and 4 is 4.
Number of erasers that Risa had in the end = 6 u
6 u = 12
1 u = 12 ÷ 6 = 2
Number of erasers that Risa and Opal had at first
= 10 u + 5 u
= 15 u
= 15 x 2
= 30
Answer(s): 30
