A jar contained $20 and $10 notes with a total value of $870. 12 pieces of $10 were exchanged for $20 notes of similar value. In the end, the number of $20 notes was the same as the $10 notes. How many $20 notes were there at first?
|
$20 |
$10 |
Before |
1 u - 6 |
1 u + 12 |
Change |
+ 6 |
- 12 |
After |
1 u |
1 u |
Total value of $20 and $10 notes remains unchanged after the exchange of notes of similar value.
Total value of 12 pieces of $10-notes
= 12 x 10
= $120
Number of $20-notes that 12 pieces of $10-notes were exchanged for
= 120 ÷ 20
= 6
In the end |
$20 |
$10 |
Total |
Number |
1 u |
1 u |
2 u |
Value |
20 |
10 |
|
Total Value |
20 u |
10 u |
30 u |
Total value of $20 and $10 notes
= 20 u + 10 u
= 30 u
30 u = 870
1 u = 870 ÷ 30 = 29
Number of $20 notes at first
= 1 u - 6
= 29 - 6
= 23
Answer(s): 23