The ratio of the number of $10-notes to $20-notes in Cindy's handbag was 1 : 4. Cindy exchanged 5 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 Cindy's handbag at first?
|
$10-notes |
$20-notes |
Before |
1 u |
4 u |
Change |
+ 10 |
- 5 |
After |
1 u + 10 |
4 u - 5 |
Value of 5 pieces of $20-notes
= 5 x 20
= $100
Number of $10-notes that Cindy exchanged for
= 100 ÷ 10
= 10
After the exchange, Cindy had an equal number of $10-notes and $20-notes.
4 u - 5 = 1 u + 10
4 u - 1 u = 10 + 5
3 u = 15
1 u = 15 ÷ 3 = 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
= 4 u
= 4 x 5
= 20
Value of $20-notes at first
= 20 x 20
= $400
Total value of $10-notes and $20-notes at first
= 50 + 400
= $450
Answer(s): $450