Many have heard it, but nobody has ever seen it, and it will not speak back until spoken to. What is it?

I am looking for a word that change both gender and number when i add the letter 'S'.

What Word am I Looking For ?

Suppose you are a girl candidate and sitting in an interview. Suddenly the interviewer asks you, 'What if one morning you wake up and find out that you are pregnant?

How will you reply to such a question?

Find the mistake in the below maths equations

A = 2
A(A-1) = 2(A-1)
A2-A = 2A-2
A2-2A = A-2
A(A-2) = A-2
A = 1

If,
9 * 8 * 7 = 65
8 * 7 * 6 = 50
7 * 6 * 5 = 37

Find
6 * 5 * 4 = ?

If you read clockwise, you can form a word by inserting three missing letters in the picture given below. Can you do it?

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

An equation has been laid down using a few matchsticks. However, as you can see, the equation is not correct. Can you correct the equation if you are allowed to add or remove 5 matchsticks?

Find out the missing number in the picture attached:

Below the four parts have been reorganised. The four partitions are exactly the same in both arrangements. Why is there a hole?