In an envelope, there were a total of 990 notes. 30% of them were $1-notes. The rest were $10-notes. Justin took out some $1-notes. As a result, the remaining $1-notes made up 10% of the notes left in the envelope. Find the total value of the $1-notes Justin took out from the envelope.
| |
$1 |
$10 |
Total |
| Before |
3x9 =
27 u |
7x9 =
63 u |
10x9 =
90 u |
| Change |
- ? |
|
|
| After |
1x7 =
7 u |
9x7 =
63 u |
10x7 =
70 u |
30% =
30100 =
310
10% =
10100 =
110
The number of $10-notes remains unchanged. Make the number of $10-notes the same. LCM of 7 and 9 is 63.
Total number of notes at first = 90 u
90 u = 990
1 u = 990 ÷ 90 = 11
Number of $1-notes that Justin took out from the envelope
= 27 u - 7 u
= 20 u
= 20 x 11
= 220
Total value of $1-notes taken out
= 220 x 1
= $220
Answer(s): $220
