Betty had some $50-notes and some $5-notes.
310 of the notes were $50-notes and the rest were $5-notes. After Betty had spent $4270 worth of $5-notes and
13 of $50-notes, she had
29 of the notes left. Find the number of $5-notes Betty had left.
| |
$50-notes |
$5-notes |
Total |
Comparing $50-notes
and $5-notes
at first |
3x9 =
27 u |
7x9 =
63 u |
10x9 =
90 u |
| Before |
3x9 =
27 u |
|
9x10 =
90 u |
| Change |
- 1x9 =
- 9 u |
- 854 |
- 7x10 =
- 70 u |
| After |
2x9=
18 u |
63 u - 854 |
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 $50-notes is repeated.
Number of $5-notes
= 4270 ÷ 5
= 854
Total number of notes spent = 9 u + 854
9 u + 854 = 70 u
70 u - 9 u = 854
61 u = 854
1 u = 854 ÷ 61 = 14
Number of $5-notes that Betty had left
= 63 u - 854
= 63 x 14 - 854
= 28
Answer(s): 28
