Can you find out the missing number?

? 4 5 3 5

9 5 7 10 3

I make a loud sound when I’m changing. When I do change, I get bigger but weigh less. What am I?

The square root of number 121 is "11". What is the square root of the number "12345678987654321."?

It is always ahead of me yet I can never see it. What is it?

You have two bottles of pills marked with labels A and B. The pills are identical. The doctor has asked you to take one A pill and one B pill daily. You cant take more or less than that.

While taking out the pills one day, you took out one pill from A and by mistake took out two from B. You have no idea which pill is which now.

You cant throw away the expensive pills. What will you do now?

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?

An express train takes 3 seconds to enter the tunnel which is 1 km long.
If it is travelling at 120 km an hour, how long will it take to pass completely through the tunnel?

A newspaper is supposed to have 60 pages, but pages 24 and 41 are missing.
Which other pages won't be there?

What has 88 keys?

Can you name four days which start with the letter 'T'?