When I get multiplied by any number, the sum of the figures in the product is always me. What am I?

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

In four steps you need to move the word 'cold' From 'warm' by replacing one alphabet at a time such that every word formed at each step is acceptable in English Dictionary.

Which Burger Is Different in below image?

You may enter, but you may not come in. I have space, but no room. I have keys, but open no lock. What am I?

I can sizzle like bacon,
I am made with an egg,
I have plenty of backbone, but lack a good leg,
I peel layers like onions, but still remain whole,
I can be long, like a flagpole, yet fit in a hole.

Give it food and it will live; give it water and it will die.

Without looking at a calendar, within a minute name, a boy's name using 5 consecutive 1st letters of 5 consecutive months

I am weightless, but you can see me. Put me in a bucket, and I'll make it lighter. What am I?

A certain street contains 100 buildings. They are numbered from 1 to 100. How many 9's are used in these numbers?