Questions

The weight of the man mg is acting on the floor. As the lift is moving up with an acceleration, say a, the man too in it is having this acceleration. The force producing this acceleration is ma. By Newton's third law, this force will have an equal reaction pressing the floor equal to ma. Therefore the total resultant reaction on the floor is mg+ma = m(g+a) which is mg, the weight of the man. So (a) is correct.

BRICS is basically an association of 5 major emerging national economies: Brazil, Russia,China, India and South Africa.

BRIC was coined in Foreign Ministerial meeting of Brazil,Russia,China and India in Newyork in Sept 2006. BRIC officialy came in existance in 2009 at Yekaterinburg,Russia.

At start group was named as BRIC, but after being formally invited by the BRIC countries to join the group, South Africa officially became a member nation on 24 December 2010, and the group was renamed BRICS.

Here given that 9 = 63, 8 = 48, 7=35, ... 

The given question follows a pattern that

9 x (9 - 2) = 9 x 7 = 63

8 x (8 - 2) = 8 x 6 = 48

7 x (7 - 2) = 7 x 5 = 35

Similarly, 4 x (4 - 2) = 4 x 2 = 8.

Common Loon

Let speed of train B be x m/s And length of train B be y m
Then length of train A is 2y m
Speed of train A = 84 × 5/18 = 210/9 m/s = 70/3 m/s
A.T.Q, (2y+y)/10 = 70/3 − x .............(i)
and (2y+y)/ 22.5 = 70/3 − 2x ................(ii)
solving (i) and (ii), y = 50 m