Yoko had some $10-notes and some $2-notes.
37 of the-notes were $10-notes and the rest were $2-notes. After Yoko had spent $638 worth of $2-notes and
23 of $10-notes, she had
310 of the notes left. Find the number of $10-notes Yoko had left.
| |
$10-notes |
$2-notes |
Total |
Comparing $10-notes
and $2-notes
at first |
3x10 =
30 u |
4x10 =
40 u |
7x10 =
70 u |
| Before |
3x10 =
30 u |
|
10x7 =
70 u |
| Change |
- 2x10 =
- 20 u |
- 319 |
- 7x7 =
- 49 u |
| After |
1x10=
10 u |
40 u - 319 |
3x7 =
21 u |
The total number of notes at first is the repeated. Make the total number of notes the same. LCM of 7 and 10 is 70.
The number of $10-notes is repeated.
Number of $2-notes
= 638 ÷ 2
= 319
Total number of notes spent = 20 u + 319
20 u + 319 = 49 u
49 u - 20 u = 319
29 u = 319
1 u = 319 ÷ 29 = 11
Number of $10-notes that Yoko had left
= 10 u
= 10 x 11
= 110
Answer(s): 110
