The ratio of the number of $2-notes to $10-notes in Min's purse was 1 : 4. Min exchanged 9 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 Min's purse at first?
|
$2-notes |
$10-notes |
Before |
1 u |
4 u |
Change |
+ 45 |
- 9 |
After |
1 u + 45 |
4 u - 9 |
Value of 9 pieces of $10-notes
= 9 x 10
= $90
Number of $2-notes that Min exchanged for
= 90 ÷ 2
= 45
After the exchange, Min had an equal number of $2-notes and $10-notes.
4 u - 9 = 1 u + 45
4 u - 1 u = 45 + 9
3 u = 54
1 u = 54 ÷ 3 = 18
Number of $2-notes at first
= 1 u
= 18
Value of $2-notes at first
= 18 x 2
= $36
Number of $10-notes at first
= 4 u
= 4 x 18
= 72
Value of $10-notes at first
= 72 x 10
= $720
Total value of $2-notes and $10-notes at first
= 36 + 720
= $756
Answer(s): $756