The ratio of the number of $5-notes to $10-notes in Opal's wallet was 1 : 4. Opal exchanged 5 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 Opal's wallet at first?
|
$5-notes |
$10-notes |
Before |
1 u |
4 u |
Change |
+ 10 |
- 5 |
After |
1 u + 10 |
4 u - 5 |
Value of 5 pieces of $10-notes
= 5 x 10
= $50
Number of $5-notes that Opal exchanged for
= 50 ÷ 5
= 10
After the exchange, Opal had an equal number of $5-notes and $10-notes.
4 u - 5 = 1 u + 10
4 u - 1 u = 10 + 5
3 u = 15
1 u = 15 ÷ 3 = 5
Number of $5-notes at first
= 1 u
= 5
Value of $5-notes at first
= 5 x 5
= $25
Number of $10-notes at first
= 4 u
= 4 x 5
= 20
Value of $10-notes at first
= 20 x 10
= $200
Total value of $5-notes and $10-notes at first
= 25 + 200
= $225
Answer(s): $225