The number of $10, $20 and $100 notes in a piggy bank is in the ratio of 1 : 9 : 7. The notes are worth $10680 altogether. Find the total number of $10 and $20 notes.
| |
$10 |
$20 |
$100 |
Total |
| Number |
1 u |
9 u |
7 u |
|
| Value |
$10 |
$20 |
$100 |
|
| Total value |
10 u |
180 u |
700 u |
$10680 |
Total value of $10, $20 and $100 notes
= 10 u + 180 u + 700 u
= 890 u
890 u = 10680
1 u = 10680 ÷ 890 = 12
Number of $10 and $20 notes
= 1 u + 9 u
= 10 u
= 10 x 12
= 120
Answer(s): 120
