Dana had some $5-notes and some $2-notes.
711 of the notes were $5-notes and the rest were $2-notes. After Dana had spent $648 worth of $2-notes and
47 of $5-notes, she had
27 of the notes left. Find the number of $2-notes Dana had left.
| |
$5-notes |
$2-notes |
Total |
Comparing $5-notes
and $2-notes
at first |
7x7 =
49 u |
4x7 =
28 u |
11x7 =
77 u |
| Before |
7x7 =
49 u |
|
7x11 =
77 u |
| Change |
- 4x7 =
- 28 u |
- 324 |
- 5x11 =
- 55 u |
| After |
3x7=
21 u |
28 u - 324 |
2x11 =
22 u |
The total number of notes at first is the repeated. Make the total number of notes the same. LCM of 11 and 7 is 77.
The number of $5-notes is repeated.
Number of $2-notes
= 648 ÷ 2
= 324
Total number of notes spent = 28 u + 324
28 u + 324 = 55 u
55 u - 28 u = 324
27 u = 324
1 u = 324 ÷ 27 = 12
Number of $2-notes that Dana had left
= 28 u - 324
= 28 x 12 - 324
= 12
Answer(s): 12
