A jar contained $10 and $20 notes with a total value of $660. 9 pieces of $20 were exchanged for $10 notes of similar value. In the end, the number of $10 notes was the same as the $20 notes. How many $10 notes were there at first?
|
$10 |
$20 |
Before |
1 u - 18 |
1 u + 9 |
Change |
+ 18 |
- 9 |
After |
1 u |
1 u |
Total value of $10 and $20 notes remains unchanged after the exchange of notes of similar value.
Total value of 9 pieces of $20-notes
= 9 x 20
= $180
Number of $10-notes that 9 pieces of $20-notes were exchanged for
= 180 ÷ 10
= 18
In the end |
$10 |
$20 |
Total |
Number |
1 u |
1 u |
2 u |
Value |
10 |
20 |
|
Total Value |
10 u |
20 u |
30 u |
Total value of $10 and $20 notes
= 10 u + 20 u
= 30 u
30 u = 660
1 u = 660 ÷ 30 = 22
Number of $10 notes at first
= 1 u - 18
= 22 - 18
= 4
Answer(s): 4