Lynn had some $100-notes and some $1-notes.
311 of the-notes were $100-notes and the rest were $1-notes. After Lynn had spent $1005 worth of $1-notes and
13 of $100-notes, she had
310 of the notes left. Find the number of $100-notes Lynn had left.
| |
$100-notes |
$1-notes |
Total |
Comparing $100-notes
and $1-notes
at first |
3x10 =
30 u |
8x10 =
80 u |
11x10 =
110 u |
| Before |
3x10 =
30 u |
|
10x11 =
110 u |
| Change |
- 1x10 =
- 10 u |
- 1005 |
- 7x11 =
- 77 u |
| After |
2x10=
20 u |
80 u - 1005 |
3x11 =
33 u |
The total number of notes at first is the repeated. Make the total number of notes the same. LCM of 11 and 10 is 110.
The number of $100-notes is repeated.
Number of $1-notes
= 1005 ÷ 1
= 1005
Total number of notes spent = 10 u + 1005
10 u + 1005 = 77 u
77 u - 10 u = 1005
67 u = 1005
1 u = 1005 ÷ 67 = 15
Number of $100-notes that Lynn had left
= 20 u
= 20 x 15
= 300
Answer(s): 300
