Vanessa had some $1-notes and some $2-notes.
712 of the notes were $1-notes and the rest were $2-notes. After Vanessa had spent $1620 worth of $2-notes and
37 of $1-notes, she had
37 of the notes left. Find the number of $2-notes Vanessa had left.
| |
$1-notes |
$2-notes |
Total |
Comparing $1-notes
and $2-notes
at first |
7x7 =
49 u |
5x7 =
35 u |
12x7 =
84 u |
| Before |
7x7 =
49 u |
|
7x12 =
84 u |
| Change |
- 3x7 =
- 21 u |
- 810 |
- 4x12 =
- 48 u |
| After |
4x7=
28 u |
35 u - 810 |
3x12 =
36 u |
The total number of notes at first is the repeated. Make the total number of notes the same. LCM of 12 and 7 is 84.
The number of $1-notes is repeated.
Number of $2-notes
= 1620 ÷ 2
= 810
Total number of notes spent = 21 u + 810
21 u + 810 = 48 u
48 u - 21 u = 810
27 u = 810
1 u = 810 ÷ 27 = 30
Number of $2-notes that Vanessa had left
= 35 u - 810
= 35 x 30 - 810
= 240
Answer(s): 240
