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

What is black when you buy it, red when you use it, and gray when you throw it away?

What is more useful when it is broken?

There is a box. The area of its top is 240 square units, the area of the front is 300 square units and the area of the end is 180 square units.

Can you calculate the dimensions of this box with the given data?

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

You bought me for dinner but never eat me. What am I?

When I asked a girl's name she told me her name is the date '07/09/2001'.

I thought for a few seconds and then I got her name. Do you?

I am eight letters long - "12345678"
My 1234 is an atmospheric condition.
My 34567 supports a plant.
My 4567 is too appropriate.
My 45 is a friendly thank-you.
My 678 is a man's name.

What word am I?

What has one letter and starts with an E?

Complete the table series riddle by finding the number that can replace "??".