The ratio of the number of $5-notes to $10-notes in Barbara's wallet was 1 : 5. Barbara exchanged 12 pieces of $10-notes for $5-notes. She then had an equal number of $5-notes and $10-notes. What was the total value of $5-notes and $10-notes in Barbara's wallet at first?
| |
$5-notes |
$10-notes |
| Before |
1 u |
5 u |
| Change |
+ 24 |
- 12 |
| After |
1 u + 24 |
5 u - 12 |
Value of 12 pieces of $10-notes
= 12 x 10
= $120
Number of $5-notes that Barbara exchanged for
= 120 ÷ 5
= 24
After the exchange, Barbara had an equal number of $5-notes and $10-notes.
5 u - 12 = 1 u + 24
5 u - 1 u = 24 + 12
4 u = 36
1 u = 36 ÷ 4 = 9
Number of $5-notes at first
= 1 u
= 9
Value of $5-notes at first
= 9 x 5
= $45
Number of $10-notes at first
= 5 u
= 5 x 9
= 45
Value of $10-notes at first
= 45 x 10
= $450
Total value of $5-notes and $10-notes at first
= 45 + 450
= $495
Answer(s): $495
