The ratio of the number of $20-notes to $50-notes in Tina's purse was 1 : 4. Tina exchanged 6 pieces of $50-notes for $20-notes. She then had an equal number of $20-notes and $50-notes. What was the total value of $20-notes and $50-notes in Tina's purse at first?
| |
$20-notes |
$50-notes |
| Before |
1 u |
4 u |
| Change |
+ 15 |
- 6 |
| After |
1 u + 15 |
4 u - 6 |
Value of 6 pieces of $50-notes
= 6 x 50
= $300
Number of $20-notes that Tina exchanged for
= 300 ÷ 20
= 15
After the exchange, Tina had an equal number of $20-notes and $50-notes.
4 u - 6 = 1 u + 15
4 u - 1 u = 15 + 6
3 u = 21
1 u = 21 ÷ 3 = 7
Number of $20-notes at first
= 1 u
= 7
Value of $20-notes at first
= 7 x 20
= $140
Number of $50-notes at first
= 4 u
= 4 x 7
= 28
Value of $50-notes at first
= 28 x 50
= $1400
Total value of $20-notes and $50-notes at first
= 140 + 1400
= $1540
Answer(s): $1540
