Find The Next Number In The Sequence

30 10 15 13 0 16 -15 ?

What can go through glass without breaking it?

Can you count the number of lines in the below picture?

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

O T T F F S S ?

A King wants to send the diamond ring to his girlfriend securely. He got multiple locks and their corresponding keys. His girlfriend does not have any keys to these locks and if he sends the key without a lock, the key can be copied in the way. How can King send the ring to his girlfriend securely?

A man has eighty-one cows ( numbered 1,2,3...81 as such). The beauty is that cow no. 1 gives 1ltr of milk, cow no. 2 gives 2ltrs of milk and so on. The man wants to equally distribute the cows among his nine sons so that each one of them gets the same quantity of milk.

John gave half of the apples he had plus one more to Jacob. He gave half of the remaining ones plus one more to James. Now, John was left with just one apple.

Can you find out how many did he have in the beginning?

Can you think of any three-dimensional shape that comprises of exactly two surfaces?

I never stop running even when I standstill. If I am formed by joining two identical bodies together, can you guess who I am?

How many triangles can you find in this given picture?