If it took eight men ten hours to build a wall, how long would it take four men to build it?

Replace the question mark with the correct number in below Picture:

I am a number I am not an odd number I am higher than 90 I am not higher than 100 If you subtract me from 100, you get nothing. What number am I?

I know a nine-letter word having only one vowel.
Do you ?

Which alphabet letter is a question?

Is the statement valid that it does not matter how much older a sibling is, eventually the younger one will be half as old as the older one?

In the given figure, you can see that four match sticks are used to form a square. Can you form five squares by using six matches?

Use only one mathematical symbol and all numbers (0-9) to get a sum of 99

I throw two dice simultaneously.

What is the probability of getting a sum as 9 of the two numbers shown?

What has many keys but can’t open a single lock?