Using four sevens (7) and a one (1) create the number 100. Except for the five numerals, you can use the usual mathematical operations (+, -, x, :), root and brackets ()

Until it is measured, not known. Yet how you miss it when it has gone. What is it?

I cannot talk, but I always reply when spoken to. What am I?

What is in seasons, seconds, centuries and minutes but not in decades, years or days?

Find the next number in the series below

21 32 54 87 131 ?

Which alphabet letter is a question?

Four cars come to a four-way stop, each coming from a different direction. They can’t decide who got there first, so they all go forward at the same time. All 4 cars go, but none crash into each other. How is this possible?

I have 50 feet long of cloth, I need to create 50 handkerchiefs each size of 1 foot. I take one minute to cut a 1-foot handkerchief. So how long will it take to cut 50 handkerchiefs?

A mother is 21 years older than her child. In exactly 6 years from now, the mother will be exactly 5 times as old as the child.
Where's the father?

I am a prime number.
The double of myself is equal to the square of me.

which number am I?