Mary had some $5-notes and some $1-notes.
512 of the notes were $5-notes and the rest were $1-notes. After Mary had spent $120 worth of $1-notes and
35 of $5-notes, she had
13 of the notes left. Find the number of $1-notes Mary had left.
| |
$5-notes |
$1-notes |
Total |
Comparing $5-notes
and $1-notes
at first |
5x1 =
5 u |
7x1 =
7 u |
12x1 =
12 u |
| Before |
5x1 =
5 u |
|
3x4 =
12 u |
| Change |
- 3x1 =
- 3 u |
- 120 |
- 2x4 =
- 8 u |
| After |
2x1=
2 u |
7 u - 120 |
1x4 =
4 u |
The total number of notes at first is the repeated. Make the total number of notes the same. LCM of 12 and 3 is 12.
The number of $5-notes is repeated.
Number of $1-notes
= 120 ÷ 1
= 120
Total number of notes spent = 3 u + 120
3 u + 120 = 8 u
8 u - 3 u = 120
5 u = 120
1 u = 120 ÷ 5 = 24
Number of $1-notes that Mary had left
= 7 u - 120
= 7 x 24 - 120
= 48
Answer(s): 48
