What does this mathematical rebus means ?

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

O T T F F S S ?

We have four gears with below features=> Both Gear A and D has 60 teeth=> Gear B has 40 teeth=> Gear C has 20 teeth=> Every two minutes, Gear B makes 25 full turns.What is the relative speed of Gear A and Gear B?

What is the four-digit number in which the first digit is one-third the second, the third is the sum of the first two, and the last is three times the second?

You may enter, but you may not come in. I have space, but no room. I have keys, but open no lock. What am I?

John has played 50 ODI's and his average is 50. How many runs should he score in his 51st ODI, so that his average score jumps to 51?

Can you find the odd number in the following?

2716, 4135, 5321 and 7145

10+10 and 11+11 can give you the same answer.

Explain how?

What does below rebus means ?

In a town, there are four houses located at different distances from each other. Following are the distances:

The third house is 60 meters apart from the first house.
The fourth house is 40 meters apart from the second house.
The third house is 10 meters nearer to the fourth house than it is to the second house.

Can you find out the distance between the fourth and the first house?