Verbal Reasoning - Mental Ability Questions

Given word is O B S E R V A N T. After making the change as given in the question, we get the following arrangement:

T N A V R E S B O. 

Mathematics is the theory of numbers and history is the theory of past events.

Hence Mathematics : Numbers :: History : Events.

Only daughter of Kamal's mother — Kamel's sister. So, Ravi's mother is Kamel's sister or Kamal is the brother of Ravi's mother

i.e., Ravi's maternal uncle. 

Whale belongs to Mammal category whereas Rat belongs to Rodent.

The pattern in the given series is +4, +9, +16, +25, ... i.e. 22,32,42,52...

The next number is 284+25 = 309.

"G is father in law of D"
G+H means G is father of H
H is either son or daughter of G
H-R means H is sister of R
R@D means R is wife of D
so H and R are sisters
and daughters of G
so husband of R i.e. D is son in law of G
or G is father in law of D

As clear from the figure itself, triangle OQX and triangle O'PX are similar.

So,

OQ/O'P = OX/O'X

=> OX = (7/9)xO'X

And since, OX + O'X = 20

=> (7/9)xO'X + O'X = 20

=> O'X = 45/4

If 'k' is number of students in P and 'l' is number of students in Q, then
From the given conditions, we have
=> k - 10 = l + 10 .......(1)
=> k + 20 = 2(l - 20) ....(2)

Solving these eqns, we get
k = 100 and l = 80.
Therefore, number of students in class Q is 80.