How can you make number one disappear by adding something to it?

I am quite hot but become too cold if you remove the first two letters. What am I?

A high school has a strange principal. On the first day, he has his students perform an odd opening day ceremony:

There are one thousand lockers and one thousand students in the school. The principal asks the first student to go to every locker and open it. Then he has the second student go to every second locker and close it. The third goes to every third locker and, if it is closed, he opens it, and if it is open, he closes it. The fourth student does this to every fourth locker, and so on. After the process is completed with the thousandth student, how many lockers are open?

What is the next number in this series?

4,12,84,3612....

A Doctor always sneezes before the rain. Doctor sneezes, Will it rain?

You are given four tennis balls and asked to arrange those balls in a manner that the distance between each one of them is exactly equal. How will you do it?

Can you name three consecutive days without using the words Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, or Sunday?

Can you find the next number in the below sequence
3 , 7 , 10 , 11 , 12 , 17 ?

In the city of Brain Teasers, 5% of people do not list their phone numbers. Now if we select random 100 people from the phone directory, then how many people selected will have unlisted phone numbers?

Take 9 from 6, 10 from 9, 50 from 40, and leave 6.

How Come ??