The ratio of the number of $2-notes to $10-notes in Betty's wallet was 1 : 4. Betty exchanged 7 pieces of $10-notes for $2-notes. She then had an equal number of $2-notes and $10-notes. What was the total value of $2-notes and $10-notes in Betty's wallet at first?
| |
$2-notes |
$10-notes |
| Before |
1 u |
4 u |
| Change |
+ 35 |
- 7 |
| After |
1 u + 35 |
4 u - 7 |
Value of 7 pieces of $10-notes
= 7 x 10
= $70
Number of $2-notes that Betty exchanged for
= 70 ÷ 2
= 35
After the exchange, Betty had an equal number of $2-notes and $10-notes.
4 u - 7 = 1 u + 35
4 u - 1 u = 35 + 7
3 u = 42
1 u = 42 ÷ 3 = 14
Number of $2-notes at first
= 1 u
= 14
Value of $2-notes at first
= 14 x 2
= $28
Number of $10-notes at first
= 4 u
= 4 x 14
= 56
Value of $10-notes at first
= 56 x 10
= $560
Total value of $2-notes and $10-notes at first
= 28 + 560
= $588
Answer(s): $588
