For more detail on weighted averages, see the following previous posts:
https://crackthecat.wordpress.com/2013/01/21/weighted-averages-1/
https://crackthecat.wordpress.com/2013/01/22/weighted-averages-2/
CAT-holics
mathematics and vocabulary for the CAT
CAT-holics 
Hi J ,
As cat is just 20 days away , can we have some blog posts which include shortcuts and alternative ways to solve questions important w.r.t to cat . Your perspective !!
TIA
I’ve already done a long series of posts on shortcuts and tricks and alternative approaches – do see these: https://crackthecat.wordpress.com/tag/paperless/
regards
J
Hey Sir,
i could get the answer ‘c’
but was not sure till i got 1/4 on paper
that diagram helped me reinforce some unsung arithmetic concepts that we so easily forget..
SIR ,
Any quadrilateral with perpendicular diagonals … its area is 1/2 * product of diagonals.
Absolutely correct. You can prove it by drawing two pairs of lines parallel to the diagionals through the vertices. At some future point I will cover quadrilaterals on the blog (don’t ask when, CAT 14 ke liye I guess:) and will discuss this concept among others…
regards
J
is it correct??????
yes sir and quadrilateral formed by parallel lines has area twice the original quad
Sir this picture is still not clear to me. Let us take the seesaw problem the distance is d and 1.5d respectively. so the mean of the distance when both the sides will be of same weight is 1.25d. So the heavier his .25d closer to the pivot and the lighter is .25d farther to the pivot. Now since the director manager problem is actually same as it is rs. 5000 further from the average and rs 15000 closer to the average. So if we just take the ratio in this case, this may indicate the seesaw problem would be solve in a similar manner by taking the ratio of .25d. But this is not the case. Since the value 15000 and 5000 shows the deflection from actual average. Little confused … Please help!!
sir, are we considering that the salary of all employees are same here, I guess number of directors or managers will only then be dependent on the salaries when we consider them to be same..or is it like we have given average so it doesn’t matter then ?
It doesn’t matter. That’s the whole point of an average; it acts as a single representative number for the individual numbers in many scenarios.
regards
J