The ratio of the number of $10-notes to $20-notes in Min's purse was 1 : 5. Min exchanged 12 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 Min's purse at first?
|
$10-notes |
$20-notes |
Before |
1 u |
5 u |
Change |
+ 24 |
- 12 |
After |
1 u + 24 |
5 u - 12 |
Value of 12 pieces of $20-notes
= 12 x 20
= $240
Number of $10-notes that Min exchanged for
= 240 ÷ 10
= 24
After the exchange, Min had an equal number of $10-notes and $20-notes.
5 u - 12 = 1 u + 24
5 u - 1 u = 24 + 12
4 u = 36
1 u = 36 ÷ 4 = 9
Number of $10-notes at first
= 1 u
= 9
Value of $10-notes at first
= 9 x 10
= $90
Number of $20-notes at first
= 5 u
= 5 x 9
= 45
Value of $20-notes at first
= 45 x 20
= $900
Total value of $10-notes and $20-notes at first
= 90 + 900
= $990
Answer(s): $990