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.

How far can you walk into the woods?

How many Watermelons are there in the below picture?

You are in a room that has three switches and a closed door. The switches control three light bulbs on the other side of the door. Once you open the door, you may never touch the switches again. How can you definitively tell which switch is connected to each of the light bulbs?

Can you make a fire with just a single stick?

If it took eight men ten hours to build a wall, how long would it take four men to build it?

You need to move three matchsticks to form three squares. Can you do it?

What does the below rebus puzzle mean?

I travel all around the world but always stay in the corner. What am I?

On a certain day, John celebrated his birthday. Two days later, his older twin brother Jacob celebrated his birthday.

Is this even possible? How can it be?