Andy, Luis and Mark had a total of 63 stamps. The ratio of the number of stamps that Luis had to the number of stamps that Mark had was 8 : 9. After Andy and Luis each gave away half of their stamps, the 3 children had 45 stamps left. How many stamps did Luis and Mark have at first?
| |
Andy |
Luis |
Mark |
Total |
| Before |
2 p |
8 u |
9 u |
63 |
| Change |
- 1 p |
- 4 u |
|
- 18 |
| After |
1 p |
4 u |
9 u |
45 |
Total number of stamps that Andy and Luis gave away
= 63 - 45
= 18
1 p + 4 u = 18 --- (1)
1 p + 4 u + 9 u = 45
1 p + 13 u = 45 --- (2)
(2) - (1)
(1 p + 13 u) - (1 p + 4 u) = 45 - 18
13 u - 4 u = 27
9 u = 27
1 u = 27 ÷ 9 = 3
Total number of stamps that Luis and Mark had at first
= 8 u + 9 u
= 17 u
= 17 x 3
= 51
Answer(s): 51
