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

I am a seven-letter word but if you remove four of my letters I will have one left. What word am I?

Can you count the number of seconds in a year?

Clue: You need to bother about calculation.

There is one thing that goes round the house and also inside the house but never even share a brief touch. What is it?

Find a 9-digit number, which you will gradually round off starting with units, then tenth, hundred etc., until you get to the last numeral, which you do not round off. The rounding alternates (up, down, up ...). After rounding off 8 times, the final number is 500000000. The original number is commensurable by 6 and 7, all the numbers from 1 to 9 are used, and after rounding four times the sum of the not rounded numerals equals 24.

In the Mexico City area, there are two Houses H1 and H2. Both H1 and H2 have two children each.
In House H1, The boy plays for Mexico Youth academy and the other child plays baseball.
In House H2, The boy Plays soccer for his school in Mexico and they recently have a newborn.

Can you prove that the probability of House-H1 having a girl child is more than that of House-H2?

I’m tall when I’m young, and I’m short when I’m old. What am I?

Can you think of any three-dimensional shape that comprises of exactly two surfaces?

An exterior architect is asked by a builder to plant seven trees in a manner that there are exactly six rows of trees in a straight line and each row has three trees in particular.

How will he do it?

I am a word that begins with the letter “i.” If you add the letter “a” to me, I become a new word with a different meaning, but that sounds exactly the same. What word am I?