Exams

51 + 52 + 53 + ...........+ 100

 = (1 + 2 + 3 + .... + 100) - (1 + 2 + 3 + ...... + 50)

 = It is in the form of n(n+1)2 series summation

= n1 = 100 , n2 = 50

=100100+12 - 5050+12

 =  (5050 - 1275) = 3775

Here the given series is 1, 3, 6, 11, 20, 37, ??,

and the logic behind the series is

1 x 2 + 1 = 3

3 x 2 + 0 = 6

6 x 2 + (-1) = 11

11 x 2 + (-2) = 20

20 x 2 + (-3) = 37

37 x 2 + (-4) = 70

Hence, the next number in the given series is 70.

$$\begin{gathered} [(K-L)2-K+L2]4K = ab \\ K2+L2-2KL-K2+L2+2KL4K= ab \end{gathered}$$

=> - 4KL/4K = a/b

=> L = - a/b

=> bL = -a

The possessive form of pronoun ‘one’ is ‘oneself’. So the phrase ‘with himself’ needs to be replaced with ‘with oneself’ to make the sentence grammatically correct. Thus, the correct formation would be, ‘One is often pleased with oneself’.

Rocket works on the principle of conservation of momentum. The rockets gain momentum equal to the momentum of the gas expelled from the engine, but in the opposite direction.

2l+bb=51      => 2l + 2b = 5b     => 3b = 2l 

b=(2/3)l

Then, Area = 216 cm² 

=> l x b = 216     => l x (2/3)l =216 

l = 18 cm.

Here Grass is to Erosion and whereas Dam is to Water.

Since Grass prevents Erosion similarly Dam prevents Water flow.

Hence, Grass : Erosion :: Dam : Water.