Jenson, Eric and George had a total of 26 erasers. The ratio of Eric's erasers to George's erasers was 2 : 3 at first. Jenson and Eric each gave away
12 of their erasers. Given that the three boys had 19 erasers left, how many erasers did Jenson have at first?
|
Jenson |
Eric |
George |
Total |
Comparing Eric and George at first |
|
2 u |
3 u |
|
Before |
2 p |
2x1 = 2 u |
3 u |
26 |
Change |
- 1 p |
-1x1 = - 1 u |
|
- 7 |
After |
1 p |
1x1 = 1 u |
3 u |
19 |
Total number of erasers that Jenson and Eric gave away
= 26 - 19
= 7
The number of erasers that Eric had at first is repeated. Make the number of erasers that Eric had at first the same. LCM of 2 and 2 is 2.
1 p + 1 u = 26 - 19
1 p + 1 u = 7
1 p = 7 - 1 u --- (1)
1 p + 1 u + 3 u = 19
1 p + 4 u = 19
1 p = 19 - 4 u --- (2)
(1) = (2)
7 - 1 u = 19 - 4 u
4 u - 1 u = 19 - 7
4 u - 1 u = 12
3 u = 12
1 u = 12 ÷ 3 = 4
Substitute 1 u = 4 into (1).
1 p = 7 - 1 u
1 p = 7 - 1 x 4
1 p = 7 - 4
1 p = 3
Number of erasers that Jenson had at first
= 2 p
= 2 x 3
= 6
Answer(s): 6