The ratio of the number of $5-notes to $10-notes in Emma's wallet was 1 : 7. Emma exchanged 4 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 Emma's wallet at first?
| |
$5-notes |
$10-notes |
| Before |
1 u |
7 u |
| Change |
+ 8 |
- 4 |
| After |
1 u + 8 |
7 u - 4 |
Value of 4 pieces of $10-notes
= 4 x 10
= $40
Number of $5-notes that Emma exchanged for
= 40 ÷ 5
= 8
After the exchange, Emma had an equal number of $5-notes and $10-notes.
7 u - 4 = 1 u + 8
7 u - 1 u = 8 + 4
6 u = 12
1 u = 12 ÷ 6 = 2
Number of $5-notes at first
= 1 u
= 2
Value of $5-notes at first
= 2 x 5
= $10
Number of $10-notes at first
= 7 u
= 7 x 2
= 14
Value of $10-notes at first
= 14 x 10
= $140
Total value of $5-notes and $10-notes at first
= 10 + 140
= $150
Answer(s): $150
