The ratio of the number of $5-notes to $10-notes in Kimberly's jar was 1 : 4. Kimberly exchanged 7 pieces of $10-notes for $5-notes. She then had an equal number of $5-notes and $10-notes. What was the total value of $5-notes and $10-notes in Kimberly's jar at first?
| |
$5-notes |
$10-notes |
| Before |
1 u |
4 u |
| Change |
+ 14 |
- 7 |
| After |
1 u + 14 |
4 u - 7 |
Value of 7 pieces of $10-notes
= 7 x 10
= $70
Number of $5-notes that Kimberly exchanged for
= 70 ÷ 5
= 14
After the exchange, Kimberly had an equal number of $5-notes and $10-notes.
4 u - 7 = 1 u + 14
4 u - 1 u = 14 + 7
3 u = 21
1 u = 21 ÷ 3 = 7
Number of $5-notes at first
= 1 u
= 7
Value of $5-notes at first
= 7 x 5
= $35
Number of $10-notes at first
= 4 u
= 4 x 7
= 28
Value of $10-notes at first
= 28 x 10
= $280
Total value of $5-notes and $10-notes at first
= 35 + 280
= $315
Answer(s): $315
