A jar contained $20 and $10 notes with a total value of $480. 6 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 - 3 |
1 u + 6 |
| Change |
+ 3 |
- 6 |
| 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 6 pieces of $10-notes
= 6 x 10
= $60
Number of $20-notes that 6 pieces of $10-notes were exchanged for
= 60 ÷ 20
= 3
| 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 = 480
1 u = 480 ÷ 30 = 16
Number of $20 notes at first
= 1 u - 3
= 16 - 3
= 13
Answer(s): 13
