Shiyun had some $2-notes and some $5-notes.
711 of the notes were $2-notes and the rest were $5-notes. After Shiyun had spent $500 worth of $5-notes and
47 of $2-notes, she had
13 of the notes left. Find the number of $5-notes Shiyun had left.
| |
$2-notes |
$5-notes |
Total |
Comparing $2-notes
and $5-notes
at first |
7x3 =
21 u |
4x3 =
12 u |
11x3 =
33 u |
| Before |
7x3 =
21 u |
|
3x11 =
33 u |
| Change |
- 4x3 =
- 12 u |
- 100 |
- 2x11 =
- 22 u |
| After |
3x3=
9 u |
12 u - 100 |
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 3 is 33.
The number of $2-notes is repeated.
Number of $5-notes
= 500 ÷ 5
= 100
Total number of notes spent = 12 u + 100
12 u + 100 = 22 u
22 u - 12 u = 100
10 u = 100
1 u = 100 ÷ 10 = 10
Number of $5-notes that Shiyun had left
= 12 u - 100
= 12 x 10 - 100
= 20
Answer(s): 20
