Replace the question mark with the correct number in the below-given picture?

A Scientist was fifty years old in the year 2000 but he was forty years old in the year 2010. How can this be possible?

PS: It has a logical answer.

Solve the mathematical equation in the picture below.

Which is heavier: a ton of bricks or a ton of feathers?

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?

Which tank will fill first?

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

O T T F F S S ?

A word I know has six letters it contains, remove one letter and 12 remain. What is it?

Count the number of triangles in the given picture.

What does man love more than life, hate more than death or mortal strife; That which contented men desire; the poor have, the rich require; the miser spends, the spendthrift saves, and all men carry to their graves?