Opal had some $50-notes and some $2-notes.
710 of the notes were $50-notes and the rest were $2-notes. After Opal had spent $92 worth of $2-notes and
47 of $50-notes, she had
47 of the notes left. Find the number of $2-notes Opal had left.
| |
$50-notes |
$2-notes |
Total |
Comparing $50-notes
and $2-notes
at first |
7x7 =
49 u |
3x7 =
21 u |
10x7 =
70 u |
| Before |
7x7 =
49 u |
|
7x10 =
70 u |
| Change |
- 4x7 =
- 28 u |
- 46 |
- 3x10 =
- 30 u |
| After |
3x7=
21 u |
21 u - 46 |
4x10 =
40 u |
The total number of notes at first is the repeated. Make the total number of notes the same. LCM of 10 and 7 is 70.
The number of $50-notes is repeated.
Number of $2-notes
= 92 ÷ 2
= 46
Total number of notes spent = 28 u + 46
28 u + 46 = 30 u
30 u - 28 u = 46
2 u = 46
1 u = 46 ÷ 2 = 23
Number of $2-notes that Opal had left
= 21 u - 46
= 21 x 23 - 46
= 437
Answer(s): 437
