A jar contained $10 and $20 notes with a total value of $660. 5 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 - 10 |
1 u + 5 |
Change |
+ 10 |
- 5 |
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 5 pieces of $20-notes
= 5 x 20
= $100
Number of $10-notes that 5 pieces of $20-notes were exchanged for
= 100 ÷ 10
= 10
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 - 10
= 22 - 10
= 12
Answer(s): 12