Xuan had an equal number of $100 and $20 notes. After spending 31 pieces of $20 and 22 pieces of $100 notes, the ratio of the $100 notes to $20 notes left was 7 : 4. Find the value of the notes left.
| |
$100 |
$20 |
| Before |
7 u + 22 |
4 u + 31 |
| Change |
- 22 |
- 31 |
| After |
7 u |
4 u |
Number of $100 notes at first = 7 u + 22
Number of $20 notes at first = 4 u + 31
The number of $100 and $20 notes at first is the same.
7 u + 22 = 4 u + 31
7 u - 4 u = 31 - 22
3 u = 9
1 u = 9 ÷ 3 = 3
Value of $100-notes left
= 7 u x 100
= 7 x 3 x 100
= $2100
Value of $20-notes left
= 4 u x 20
= 4 x 3 x 20
= $240
Value of notes left
= 2100 + 240
= $2340
Answer(s): $2340
