Opal had some $100-notes and some $5-notes.
78 of the-notes were $100-notes and the rest were $5-notes. After Opal had spent $495 worth of $5-notes and
17 of $100-notes, she had
57 of the notes left. Find the number of $100-notes Opal had left.
| |
$100-notes |
$5-notes |
Total |
Comparing $100-notes
and $5-notes
at first |
7x7 =
49 u |
1x7 =
7 u |
8x7 =
56 u |
| Before |
7x7 =
49 u |
|
7x8 =
56 u |
| Change |
- 1x7 =
- 7 u |
- 99 |
- 2x8 =
- 16 u |
| After |
6x7=
42 u |
7 u - 99 |
5x8 =
40 u |
The total number of notes at first is the repeated. Make the total number of notes the same. LCM of 8 and 7 is 56.
The number of $100-notes is repeated.
Number of $5-notes
= 495 ÷ 5
= 99
Total number of notes spent = 7 u + 99
7 u + 99 = 16 u
16 u - 7 u = 99
9 u = 99
1 u = 99 ÷ 9 = 11
Number of $100-notes that Opal had left
= 42 u
= 42 x 11
= 462
Answer(s): 462
