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

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?

There's one "sport" in which neither the spectators nor the participants know the score or the leader until the contest ends.

What is it?

Using Only Five 5's and any mathematical operator make sum as 37

During which month do people sleep the least?

There was a strange boy who was born before his father. How can this be possible?

I am sure no one can have two things for dinner. what are they?

Find the mistake in the below maths equations

A = 2
A(A-1) = 2(A-1)
A2-A = 2A-2
A2-2A = A-2
A(A-2) = A-2
A = 1

How can you make the following equation true by drawing only one straight line: 5+5+5=550 ?

Some friends went on a vacation to a resort. It was raining heavily and it kept raining for thirteen days.

When it rained in the morning, the afternoon was beautiful and when it rained in the afternoon, the day was blessed with a clear morning.

Overall, the friends experienced eleven nice mornings and twelve nice afternoons. Can you find out the number of days they spent on vacation?