Kathy had some $2-notes and some $5-notes.
910 of the notes were $2-notes and the rest were $5-notes. After Kathy had spent $575 worth of $5-notes and
59 of $2-notes, she had
49 of the notes left. Find the number of $5-notes Kathy had left.
| |
$2-notes |
$5-notes |
Total |
Comparing $2-notes
and $5-notes
at first |
9x9 =
81 u |
1x9 =
9 u |
10x9 =
90 u |
| Before |
9x9 =
81 u |
|
9x10 =
90 u |
| Change |
- 5x9 =
- 45 u |
- 115 |
- 5x10 =
- 50 u |
| After |
4x9=
36 u |
9 u - 115 |
4x10 =
40 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 $2-notes is repeated.
Number of $5-notes
= 575 ÷ 5
= 115
Total number of notes spent = 45 u + 115
45 u + 115 = 50 u
50 u - 45 u = 115
5 u = 115
1 u = 115 ÷ 5 = 23
Number of $5-notes that Kathy had left
= 9 u - 115
= 9 x 23 - 115
= 92
Answer(s): 92
