The ratio of the number of $10-notes to $20-notes in Xandra's handbag was 1 : 3. Xandra exchanged 4 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 Xandra's handbag at first?
|
$10-notes |
$20-notes |
Before |
1 u |
3 u |
Change |
+ 8 |
- 4 |
After |
1 u + 8 |
3 u - 4 |
Value of 4 pieces of $20-notes
= 4 x 20
= $80
Number of $10-notes that Xandra exchanged for
= 80 ÷ 10
= 8
After the exchange, Xandra had an equal number of $10-notes and $20-notes.
3 u - 4 = 1 u + 8
3 u - 1 u = 8 + 4
2 u = 12
1 u = 12 ÷ 2 = 6
Number of $10-notes at first
= 1 u
= 6
Value of $10-notes at first
= 6 x 10
= $60
Number of $20-notes at first
= 3 u
= 3 x 6
= 18
Value of $20-notes at first
= 18 x 20
= $360
Total value of $10-notes and $20-notes at first
= 60 + 360
= $420
Answer(s): $420