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April 12th, 2018, 07:16 PM   #1
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A Milk solution of 60 litres contain....

A Milk solution of 60 litres contains 80% milk. How many litres of another milk solution containing 90% milk should be added to make an 84% milk solution? [Ans: 40 lit]

I tried: $\dfrac {80}{100}\times \dfrac {M}{60} $

= $\dfrac {M}{25}$

calculation of second sentence:

$\dfrac {M}{60}\times \dfrac {84}{100}$

= $\dfrac {21 M}{1500}$

calculation of first part in second sentence:

$ \dfrac {M}{60}\times \dfrac {90}{100}$

Final equation: $ \dfrac {M}{60}\times \dfrac {90}{100} = \dfrac {M}{25} - \dfrac {21 M}{1500}$

I gone too far, is my approach right or wrong? if wrong, tell me the correct procedure.

Last edited by Ganesh Ujwal; April 12th, 2018 at 07:24 PM.
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April 12th, 2018, 07:58 PM   #2
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Code:
  60   :  80
   x    :  90
------------
60+x :  84
(80*60 + 90*x) / (60 + x) = 84
4800 + 90x = 84(60 + x)
4800 + 90x = 5040 + 84x

Can you finish it?
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April 12th, 2018, 08:11 PM   #3
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Quote:
Originally Posted by Denis View Post
60.....5040 + 84x

Can you finish it?
You need to tell me why is my approach wrong otherwise feel free to ignore this question.

I am following this equation:

$\text{Concentration} = \dfrac{\text{Amount of milk}}{\text{Total amount of liquid}}$

Last edited by Ganesh Ujwal; April 12th, 2018 at 08:14 PM.
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April 13th, 2018, 04:30 AM   #4
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Code:
QUANTITY  PERCENTAGE
       a      :        u
       b      :        v
 --------------------
     a+b    :       w
FORMULA: (a*u + b*v) / (a+b) = w

I agree with you when you said you're not dumb,
so I'm sure you can figure out (by using above)
why your approach is not the correct approach.
Have a good day.
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