Diana had some $2-notes and some $10-notes.
78 of the-notes were $2-notes and the rest were $10-notes. After Diana had spent $3120 worth of $10-notes and
27 of $2-notes, she had
110 of the notes left. Find the number of $2-notes Diana had left.
| |
$2-notes |
$10-notes |
Total |
Comparing $2-notes
and $10-notes
at first |
7x5 =
35 u |
1x5 =
5 u |
8x5 =
40 u |
| Before |
7x5 =
35 u |
|
10x4 =
40 u |
| Change |
- 2x5 =
- 10 u |
- 312 |
- 9x4 =
- 36 u |
| After |
5x5=
25 u |
5 u - 312 |
1x4 =
4 u |
The total number of notes at first is the repeated. Make the total number of notes the same. LCM of 8 and 10 is 40.
The number of $2-notes is repeated.
Number of $10-notes
= 3120 ÷ 10
= 312
Total number of notes spent = 10 u + 312
10 u + 312 = 36 u
36 u - 10 u = 312
26 u = 312
1 u = 312 ÷ 26 = 12
Number of $2-notes that Diana had left
= 25 u
= 25 x 12
= 300
Answer(s): 300
