Friday, March 26, 2010

Ratio P6 A002

In a bag of notes, the number of $2, $5 and $10-notes are in ratio of 22 : 7 : 3. 5/11 of the $2-notes and 71 of $5-notes are taken out. The remaining notes are worth $624. How many $10-notes are there?

Original number of $2 is 22 units. So convert the remaining fraction in order to compare to 22 units.
5/11 x 2/2 = 10/22 
Convert the 71 $5 notes to amount.
71 x 5 = $355

  $2            $5         $10     Total
-----------------------------------------
  22   :        7        :    3
- 10         -$355
-----------------------------------------
  12   :   7 - $355   :    3
-----------------------------------------
  24       35 - $355      30     $624    Convert number of notes
------------------------------------------  to amount.

24 + 35 + 30 = 89
89 u --> 624 + 355 = 979
1 u --> 979 ÷ 89 = 11

3 u --> 3 x 11 = 33
If you are worried that marks may be deducted, you can always find 30 u to get $330. Then divide by 10 to get 33 $10 notes.

There are 33 $10 notes.

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