Cathy had some $1-notes and some $10-notes.
710 of the-notes were $1-notes and the rest were $10-notes. After Cathy had spent $6250 worth of $10-notes and
57 of $1-notes, she had
29 of the notes left. Find the number of $1-notes Cathy had left.
| |
$1-notes |
$10-notes |
Total |
Comparing $1-notes
and $10-notes
at first |
7x9 =
63 u |
3x9 =
27 u |
10x9 =
90 u |
| Before |
7x9 =
63 u |
|
9x10 =
90 u |
| Change |
- 5x9 =
- 45 u |
- 625 |
- 7x10 =
- 70 u |
| After |
2x9=
18 u |
27 u - 625 |
2x10 =
20 u |
The total number of notes at first is the repeated. Make the total number of notes the same. LCM of 10 and 9 is 90.
The number of $1-notes is repeated.
Number of $10-notes
= 6250 ÷ 10
= 625
Total number of notes spent = 45 u + 625
45 u + 625 = 70 u
70 u - 45 u = 625
25 u = 625
1 u = 625 ÷ 25 = 25
Number of $1-notes that Cathy had left
= 18 u
= 18 x 25
= 450
Answer(s): 450
