The ratio of the number of $10-notes to $20-notes in Elyse's jar was 1 : 7. Elyse exchanged 10 pieces of $20-notes for $10-notes. She then had an equal number of $10-notes and $20-notes. What was the total value of $10-notes and $20-notes in Elyse's jar at first?
| |
$10-notes |
$20-notes |
| Before |
1 u |
7 u |
| Change |
+ 20 |
- 10 |
| After |
1 u + 20 |
7 u - 10 |
Value of 10 pieces of $20-notes
= 10 x 20
= $200
Number of $10-notes that Elyse exchanged for
= 200 ÷ 10
= 20
After the exchange, Elyse had an equal number of $10-notes and $20-notes.
7 u - 10 = 1 u + 20
7 u - 1 u = 20 + 10
6 u = 30
1 u = 30 ÷ 6 = 5
Number of $10-notes at first
= 1 u
= 5
Value of $10-notes at first
= 5 x 10
= $50
Number of $20-notes at first
= 7 u
= 7 x 5
= 35
Value of $20-notes at first
= 35 x 20
= $700
Total value of $10-notes and $20-notes at first
= 50 + 700
= $750
Answer(s): $750
