A jar contained $20 and $10 notes with a total value of $570. 4 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 - 2 |
1 u + 4 |
Change |
+ 2 |
- 4 |
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 4 pieces of $10-notes
= 4 x 10
= $40
Number of $20-notes that 4 pieces of $10-notes were exchanged for
= 40 ÷ 20
= 2
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 = 570
1 u = 570 ÷ 30 = 19
Number of $20 notes at first
= 1 u - 2
= 19 - 2
= 17
Answer(s): 17