The ratio of the number of $2-notes to $10-notes in Zara's purse was 1 : 7. Zara exchanged 10 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 Zara's purse at first?
| |
$2-notes |
$10-notes |
| Before |
1 u |
7 u |
| Change |
+ 50 |
- 10 |
| After |
1 u + 50 |
7 u - 10 |
Value of 10 pieces of $10-notes
= 10 x 10
= $100
Number of $2-notes that Zara exchanged for
= 100 ÷ 2
= 50
After the exchange, Zara had an equal number of $2-notes and $10-notes.
7 u - 10 = 1 u + 50
7 u - 1 u = 50 + 10
6 u = 60
1 u = 60 ÷ 6 = 10
Number of $2-notes at first
= 1 u
= 10
Value of $2-notes at first
= 10 x 2
= $20
Number of $10-notes at first
= 7 u
= 7 x 10
= 70
Value of $10-notes at first
= 70 x 10
= $700
Total value of $2-notes and $10-notes at first
= 20 + 700
= $720
Answer(s): $720
