Buy me, smell me or deliver me, I do not change.

Who am I?

Name a key which is hardest to turn.

A brand new Mobile Phone was on sale at 20% as a promotional offer. By what per cent must the Mobile price be increased to sell it at the original price again?

Prove that twice of ten is the same as twice of eleven.

There is a five-letter word which has 3 consonants(all are same) and 2 different vowels.
Also, something wrong is associated with the word.

Can you name it?

What is the fewest number of coins that would be required in order to make sure each and every coin touches exactly three other coins?

Sally lives in a place where six months of the year is mild summer and the temperature drops significantly the other six months. She owns a lake where there is a small island. She wants to build a house on the island and needs to get materials there. She doesn’t have a boat, plane, or anything to transport them to the island. How does Sally solve this problem?

An ape is trying to climb on a pole that is 60 feet high. Due to the slippery surface, the ape climbs 3 feet in a minute only to slip back 2 feet.

How much time do you think the monkey will take to reach the top of the pole?

The more of this there is, the less you see. What is it?

By moving just one matchstick, you need to make the below statement true. Can you do it?