What is always in front of you but can’t be seen?

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

How many words can a pen with half refill write?

I have a five and a three-gallon jar. Assuming there is an infinite supply of water, how can I measure one-gallon water?

What makes this number unique: 8,549,176,320?

Find the hidden tiger in the given optical illusion ?

You have 10 balls with you. A friend of yours out of nowhere asks you to place those ten balls in five lines such that each of the lines has exactly 4 balls on them. He needs to check your intelligence. Prove him by doing the task.

What is in seasons, seconds, centuries and minutes but not in decades, years or days?

What is red and smells like blue paint?

You are given with the following sum. Each of the letters can be decoded as a digit. If we tell you that D = 5, then can you solve it entirely?

DONALD
+GERALD
=ROBERT