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

O T T F F S S ?

What's the only room from which no one can enter or leave

People are waiting in line to board a 100-seat aeroplane. Steve is the first person in the line. He gets on the plane but suddenly can't remember what his seat number is, so he picks a seat at random. After that, each person who gets on the plane sits in their assigned seat if it's available, otherwise, they will choose an open seat at random to sit in. The flight is full and you are last in line. What is the probability that you get to sit in your assigned seat?

Can you spot the hidden clock in this family photo? Only the most eagle-eyed will find it!

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?

Find out a multi-digit number that if multiplied by the number 9 or any of its multiplications products (i.e. 18, 27, 36, 45,..) will result in the multiplication factor repeated (n) number of times.

I have four wings but can't fly.
I express no emotions.
I am found on the exact spot every time you look.
I keep toiling away with a little sound.

Do you know what am I?

Can you place six X (crosses) in below board without making three in a row in any way ?

If a wheel has 54 spokes, how many spaces are there between the spokes?

We have two identical balls in terms of diameter and weight. However, one of them is solid and the other is hollow.

Without knocking the ball, can you find the solid ball?