Aptitude - Alligation or Mixture - Discussion

Discussion Forum : Alligation or Mixture - General Questions (Q.No. 1)
1.
A vessel is filled with liquid, 3 parts of which are water and 5 parts syrup. How much of the mixture must be drawn off and replaced with water so that the mixture may be half water and half syrup?
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Answer: Option
Explanation:

Suppose the vessel initially contains 8 litres of liquid.

Let x litres of this liquid be replaced with water.

Quantity of water in new mixture = 3 - 3x + x litres
8

Quantity of syrup in new mixture = 5 - 5x litres
8

3 - 3x + x = 5 - 5x
8 8

5x + 24 = 40 - 5x

10x = 16

x = 8 .
5

So, part of the mixture replaced = 8 x 1 = 1 .
5 8 5

Discussion:
198 comments Page 10 of 20.

Usha said:   1 decade ago
How we get 5x+24=40-5x?

K.S PAL said:   1 decade ago
A container is filed with 3 part water & 5 parts syrup, so total we have 8 parts or mathematically we can say,

3/8 water.
5/8 syrup.

Suppose we withdraw x parts of mixture then this will contain,

3/8(x) water.
5/8(x) syrup.

Now we have to add same amount of water the amount of water and syrup will be equal, so mathematically.

3/8-3/8(x) +x = 5/8-5/8(x).

It will give x = 1/5.

Jerry said:   1 decade ago
Why do we add y in this step 3/8[x-y] + y = 5/8[x-y] ?

The rest of the steps are perfectly understood! Thanks :),.

Mohan said:   1 decade ago
Hey guys I think this is useful formula for this question:

1/2(difference in parts/greater part).

1/2(5-3/5).

1/5.

Anonymous said:   1 decade ago
From where did you get 1/8 in finding the final result?

Yogita said:   1 decade ago
How we find the % of thing?

Vaishali Sharma said:   1 decade ago
There has to be a direct formula for this.

Anyone has it?

Prabha prabcuteatgmaildotcom said:   1 decade ago
Mean litre, m = (l+s)/2.
m = 4.

Proportion x = (l-m)/l.
x = 5-4/5.
x = 1/5.

Pure and Simple.

Mohi said:   1 decade ago
I cannot understand. Its so difficult for me. Please explain in another way.

Harleen said:   1 decade ago
Let there be 8 liters of solution, in which 3/8 liter be water and 5/8 lt be syrup. As we can see syrup is more than water so of course some syrup is to be replaced with water. As it is a solution and we can't remove only syrup or water so we have to remove the whole solution and replace it with water.

Now using ratio and proportion (5-(5x/8))/(3-(3x/8)+x) = 1/1.

As some part of syrup will be removed we also have to remove water as i have told that we are replacing some part of whole solution with water thats why we are subtracting 5x/8, 3x/8 from numerator and denominator respectively, now after removing solution we have add equal quantity of water thats why we will add water in denominator which will be equivalent to the quantity of the solution removed i.e 5x/8+3x/8=x. On the RHS side value will be as we want both the syrup and water in same proportion i.e 1/1.


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