Xandra had some $5-notes and some $2-notes.
711 of the notes were $5-notes and the rest were $2-notes. After Xandra had spent $1170 worth of $2-notes and
67 of $5-notes, she had
110 of the notes left. Find the number of $2-notes Xandra had left.
| |
$5-notes |
$2-notes |
Total |
Comparing $5-notes
and $2-notes
at first |
7x10 =
70 u |
4x10 =
40 u |
11x10 =
110 u |
| Before |
7x10 =
70 u |
|
10x11 =
110 u |
| Change |
- 6x10 =
- 60 u |
- 585 |
- 9x11 =
- 99 u |
| After |
1x10=
10 u |
40 u - 585 |
1x11 =
11 u |
The total number of notes at first is the repeated. Make the total number of notes the same. LCM of 11 and 10 is 110.
The number of $5-notes is repeated.
Number of $2-notes
= 1170 ÷ 2
= 585
Total number of notes spent = 60 u + 585
60 u + 585 = 99 u
99 u - 60 u = 585
39 u = 585
1 u = 585 ÷ 39 = 15
Number of $2-notes that Xandra had left
= 40 u - 585
= 40 x 15 - 585
= 15
Answer(s): 15
