Let;
Milk = M L
Cream = C L
Given Total = (M+C) = 60 L

Use the concept of Weighted Average;
5M + 75C = 50(M+C)
5M + 75(60-M) = 50(60) .................. [Since, M+C = 60]
4500 -70M = 3000
70M = 1500
M = 21.428 L

Hence, option B

Hi,

It is better to use options for such question. Let milk be M and cream be C
As there is 50% butterfat in the mixture. Thus, there is 30 Liters of butterfat in the total mixture

A. 20.00- If it is 20 liters of Milk then 20*0.05=1 liter of cream. 40 liters of cream then 40*0.75=30 liters. Thus, 30+1=31 liters, which is greater than required value.

B. 21.43- 21.43*0.05= 1.0715 liters of butterfat. 38.57 liters of cream then 38.57*0.75=28.927 liters of Butterfat
Thus 1.0715+28.9275=29.999 close to 30

As the other options are far greater than 21.43 option B is the best possible answer.

IMO B

Hope this helps!

Sure, this is a nice approach too.
But, don't you think that will require more time to solve each option rather than solving the exact option choice?

Hi,

Thanks! This was just another approach. I think if someone does not knows how to solve to an exact option choice(Even I didn't know. LOL ), wouldn't it be better to get an answer right by knowing just another approach using the options. And you don't have to try all the options all the time.

P.s. It took me less than the avg time required to solve this question. The step by step approach is surely important but not the most important thing.

Regards

There is not the best approach. it depends

However, the solution above using weighted average in this scenario is the best approach

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