Sarah had some $10-notes and some $5-notes.
25 of the notes were $10-notes and the rest were $5-notes. After Sarah had spent $230 worth of $5-notes and
12 of $10-notes, she had
23 of the notes left. Find the number of $5-notes Sarah had left.
| |
$10-notes |
$5-notes |
Total |
Comparing $10-notes
and $5-notes
at first |
2x3 =
6 u |
3x3 =
9 u |
5x3 =
15 u |
| Before |
2x3 =
6 u |
|
3x5 =
15 u |
| Change |
- 1x3 =
- 3 u |
- 46 |
- 1x5 =
- 5 u |
| After |
1x3=
3 u |
9 u - 46 |
2x5 =
10 u |
The total number of notes at first is the repeated. Make the total number of notes the same. LCM of 5 and 3 is 15.
The number of $10-notes is repeated.
Number of $5-notes
= 230 ÷ 5
= 46
Total number of notes spent = 3 u + 46
3 u + 46 = 5 u
5 u - 3 u = 46
2 u = 46
1 u = 46 ÷ 2 = 23
Number of $5-notes that Sarah had left
= 9 u - 46
= 9 x 23 - 46
= 161
Answer(s): 161
