Maths for CLAT #2: Tricks in Averages and Ratio and Proportions

For cracking CLAT with a good score, maths cannot be ignored. You have to be really fast to solve 20 questions in about 12 minutes(which is the ideal situation). In this post we attempt to familiarize you with some tricks which will help you to be quicker and with accuracy in maths section.

A short trick in Averages

This is one of the most asked areas in CLAT .

Suppose there is a question where the average weight of a class consisting of 15 students is 25 kilograms and if a teacher is added then the average increases by 4 kgs. You have to find weight of teacher.

Now such questions are easy per se, but by using a short cut method, these become easier .However, practice a lot before you actually use any trick, else you won’t be able to use the same.

Now, in questions like this one, just multiply the new number. of people in class, i.e.16 with increase in average weight of class, 4. Your equation should be like 16 X 4 = 64. Now add number of students in this product, here is you answer, i.e. 25 + 64 = 89. This is the answer.

Ratio and Proportion

I When A : B = m : n, and B : C = p : q. Then A : B : C = mp : pn :nq.

Such questions are also widely asked in examinations like CLAT, so make sure that you don’t mug up such rules but your mind should absorb and internalize such tricks.

II When A : B = m : n, B : C = p : q, and C : D = r : s. Then A : B : C : D = mpr: npr : nqr : nqs.

Try to find a particular pattern being followed in both the tricks so that you don’t haveto memorize the equation.

III Suppose there are two containers and in one container, oil and water are in ratio p : q and in other container oil and water are in ration r : s. Now if both the containers are emptied in a third container then in third container the ratio between oil and water will be:

{ p/p+q + r/r+s} : {q/p+q + s/r+s}

IV This is very important as it saves a lot of time, and questions of this type are frequently asked in exams like CLAT. Suppose that in a container the ratio between oil and water is p : q and the quantity is x litres. And now if you have to find the amount of water to be mixed so that the ratio becomes a : b, then it can be solved by following method:

x(pb – qa)/a(p + q)

These formula are not for mugging up but need to be practiced intensely so that you internalize these, else the pressure of CLAT will mess it up.

We shall meet again with some new tricks. Till then, ciao!

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