Dana had some $50-notes and some $2-notes.
59 of the-notes were $50-notes and the rest were $2-notes. After Dana had spent $680 worth of $2-notes and
15 of $50-notes, she had
512 of the notes left. Find the number of $50-notes Dana had left.
| |
$50-notes |
$2-notes |
Total |
Comparing $50-notes
and $2-notes
at first |
5x4 =
20 u |
4x4 =
16 u |
9x4 =
36 u |
| Before |
5x4 =
20 u |
|
12x3 =
36 u |
| Change |
- 1x4 =
- 4 u |
- 340 |
- 7x3 =
- 21 u |
| After |
4x4=
16 u |
16 u - 340 |
5x3 =
15 u |
The total number of notes at first is the repeated. Make the total number of notes the same. LCM of 9 and 12 is 36.
The number of $50-notes is repeated.
Number of $2-notes
= 680 ÷ 2
= 340
Total number of notes spent = 4 u + 340
4 u + 340 = 21 u
21 u - 4 u = 340
17 u = 340
1 u = 340 ÷ 17 = 20
Number of $50-notes that Dana had left
= 16 u
= 16 x 20
= 320
Answer(s): 320
