Look at the below sequence of letters and tell us what the next letter should be:

O T T F F S S ?

Accidentally, two trains are running in the opposite direction and enter a tunnel that is 200 miles long. A supersonic bird that has fled the lab and taken shelter in the tunnel starts flying from one train towards the other at a speed of 1000 mph. As soon as it reaches the second train, he starts flying back to avoid collision and meets the first train again at the other end. The bird keeps flying to and fro till the trains collide with each other.

What is the total distance that the supersonic bird has traveled till the trains collided?

What is the longest word in the dictionary?

A word I know,
Six letters contain,
Subtract just one,
And twelve is what remains.

There are two dice with empty faces in front of you and a marker. You can mark any number on each of the faces of the two dice, but you have to display all 31 days of the month using the two of them.

Which numbers will you mark on which dice so that you can easily depict all the dates of the month?

How many times in a given day, minutes and hour clock comes in a straight line ?

What will be the best approach to finding all the prime numbers less than 75 that leave an odd reminder when we divide them with 5?

In the given figure, move three matchsticks so that the resulting figure contains two rectangles.

ENEMY = 2 * LINK
LINK + 2 = HELL

Then what will be TAXI + HELL? Select from the options below:
a) ROTTEN
b) DANGER
c) HEAVEN
4) MORTAL

Can you count the number of squares in the given picture?