10+10 and 11+11 can give you the same answer.

Explain how?

I have one of the three numbers: 1, 2, or 3 in my mind. I speak only truth. You can ask me just one question for which I will only reply in yes or no or don't know. What question will you ask from me so that you are able to know the number?

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

What always comes into a house through the keyhole?

Find out the missing number in the picture attached:

Things are just as they seem, right? Well, check again.
Can you count the number of tigers in this picture ?

Two guards were on duty outside a barracks. One faced up the road to watch for anyone approaching from the North. The other looked down the road to see if anyone approached from the South. Suddenly one of them said to the other, "Why are you smiling?"

How did he know his companion was smiling?

If we change the South-East direction into North and North-East into West and all others similarly.
Can you find out which direction will be in the place of South-West direction?

A man fell off a smuggling boat into deep water. He could not swim and he was not wearing anything to keep him afloat. It took 30 minutes for the people on the boat to realize someone was missing. The missing man was rescued two hours later on the return trip. Why didn't he drown? Note:- He didn't know swimming, the sea was deep, and He wasn't holding anything

I’m tall when I’m young, and I’m short when I’m old. What am I?