23 of Mark's savings comprised of 5-cent coins and 10-cent coins. Mark used some 5-cent coins to purchase a flying saucer. The number of 10-cent coins left was 40% more than the number of 5-cent coins left. Given that Mark had 40 more 10-cent coins than 5-cent coins left in the end, find the amount of money Mark spent on the flying saucer.
|
5-cent coins |
10-cent coins |
Before |
2x7 = 14 u |
1x7 = 7 u |
Change |
- 9 u |
|
After |
5x1 = 5 u |
7x1 = 7 u |
Fraction of Mark's savings that comprised of 10-cent coins
= 1 -
23=
13Number of 10-cents coins in the end in percentage
= 100% + 40%
= 140%
140% =
140100 =
75Number of 10-cent coins remains unchanged. Make the number of 10-cent coins the same. LCM of 1 and 7 is 7.
Number of more 10-cent coins than 5-cent coins
= 7 u - 5 u
= 2 u
2 u = 40
1 u = 40 ÷ 2 = 20
Number of 5-cent coins spent on the flying saucer
= 14 u - 5 u
= 9 u
= 9 x 20
= 180
Amount that Mark spent on the flying saucer
= 180 x 0.05
= $9
Answer(s): $9