81 x 9 = 801. What must you do to make the this equation true?

In my garden, I have many trees but only one of them is the mango tree. In these mango trees, there are some mangoes(as expected).

But after a strong wind, there are neither mangoes on the tree nor on the ground. Explain?

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?

Can you solve this amazing hard number series problem?
7, 8, 10, 12, 16, 18 ?

If I put in one bird per cage, I have one bird too many. If I put in two bird per cage, I have one cage too many. How many cages and birds do I have?

What goes up but never comes down?

What has one letter and starts with an E?

What can you see in the middle of March and April that you can never see in any other month?

Two in a corner, one in a room, zero in a house, but one in a shelter. What am I?

Can you make a six-letter word using the letters N, A and B ?