Averages, Ratio & Proportion : A Few Tricks of The Trade

Gone are the days when the “slow and the stea­dy” used to win the race, now it’s just the “fast and the furious” who snatch all the cakes and especially in the case of CLAT, you aren’t supposed be just ‘fast and furious’ but more importantly accurate!. In this short write up I would like to share with you some tricks which magically get rid of many lengthy and boring steps without affecting accuracy. In an examination like CLAT, which demands you to solve 200 questions in 120 minutes, which includes 20 maths questions for which you’re not expected to utilize more than 12-15 minutes (ideally), you need to be really fast. Now let me come to the point and share some tricks which can come handy for CLAT so as to enable you to do this section with full accuracy and this will certainly giveyou an edge.

Averages

This is certainly one of the most asked areas in CLAT and one should do this section thoroughly. Suppose there is a question where the average weight of a class consisting of 20 students is 40 kilograms and if a teacher is added then the average increases by 2 kgs. Now such questions are very easy but by using a short cut method, it turns out to be extremely easy.However, always remember that the tricks are also steps in themselves, so practice a lot before you actually use them, so that you improve your overall efficiency.

Now, in questions like this one, just multiply the new number. of people in class, i.e. 21 with old average weight, i.e. 40. The product is 840. Then, multiply increase in average weight with new no. of people in class, i.e. 21. Your equation should be like 21 X 2 = 42. Now add previous product and this product, here is you answer, i.e. 840 + 42 = 882.

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.

Explanation: i) A : B = 1 : 2

ii) B : C = 3 : 4

iii) C : D = 5 : 6

Then A : B : C : D = 1*3*5 : 2*3*5 : 2*4*5 : 2*4*6

And, A : B : C : D : = 15 : 30 : 40 : 48

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

Explanation: If there are two containers and in one container oil and water are in ration 1: 2, and in second container oil and water are in ration 1: 3. Now both the containers are emptied in a third container, then the ration of oil and water in the third container will be: 1/(1 + 2) +1/(1 + 3) : 2/(1 + 2) + 3/(1 +3)

Now, it comes like 1/3 + 1/4 : 2/3 + 3/4

= 7/12 : 17/12

=7 : 17.

x(pb – qa)

a(p + q)

Explanation: In a container there is 40L mixture of milk and water, which are in the ration 3:1. How much water is to be mixed to make the ration 2:1.

Now: 40(3*1 – 2*1) =40(1) = 40 = 5L

2(1 + 3) 4*2 8

I will reiterate the same thing again that these formulae are not for mugging up but these need to be practised enough number of types so that you know the basic funda working behind it and moreover if you are still not able to absorb it you want to cram then first of all change the each formulae in such a way that each formula has different set of alphabets used in it otherwise the pressure of CLAT will make you to mess it up. Now, good luck to all of you and we will try to come up with new time saving tricks so that you people have better chances of making it through.

Again good luck.
Shubhank Sanjeev,
NALSAR University of Law.