The ratio of the number of $2-notes to $10-notes in Irene's bag was 1 : 4. Irene 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 Irene's bag at first?
|
$2-notes |
$10-notes |
Before |
1 u |
4 u |
Change |
+ 50 |
- 10 |
After |
1 u + 50 |
4 u - 10 |
Value of 10 pieces of $10-notes
= 10 x 10
= $100
Number of $2-notes that Irene exchanged for
= 100 ÷ 2
= 50
After the exchange, Irene had an equal number of $2-notes and $10-notes.
4 u - 10 = 1 u + 50
4 u - 1 u = 50 + 10
3 u = 60
1 u = 60 ÷ 3 = 20
Number of $2-notes at first
= 1 u
= 20
Value of $2-notes at first
= 20 x 2
= $40
Number of $10-notes at first
= 4 u
= 4 x 20
= 80
Value of $10-notes at first
= 80 x 10
= $800
Total value of $2-notes and $10-notes at first
= 40 + 800
= $840
Answer(s): $840