How many sides does a circle have?

Before Mount Everest was discovered, what was the highest mountain in the world?

What is the next shape from answers A, B, C, and D figure?

Can you move 2 matchsticks to form four equal sized squares.

At my favorite fruit stand,
an orange costs 18,
a pineapple costs 27,
and a grape costs 15.
Using the same logic, can you tell how much a mango costs?

I know a ten-letter word in the English language which can be typed using only the top rows of the computer keyboard.

Identify Me

Hint1: I am a god
Hint 2: I am a planet
Hint 3: measurer of heat

Two boys wish to cross a river. The only way to get to the other side is by boat, but that boat can only take one boy at a time. The boat cannot return on its own, there are no ropes or similar tricks, yet both boys manage to cross using the boat.

How?

While handling a project, the landscaper is asked by the owner of the mansion that he wants four trees in front of his mansion that are exactly equidistant from each other.

How will he do it?

It's a 7-letter word.
If we remove 1 letter from it, it remains the same.
If we remove 2 letters from it, it remains the same.
If we remove 3 letters from it, it remains the same.
If we remove all the letters from it, still it remains the same.
What is it?