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

What Word am I Looking For ?

Manish has to secure 40% marks to pass his B.tech final exams.
He got just 40 marks and failed by 40-marks.

What is the maximum marks?

Twice ten are six of us,

Six are but three of us,

Nine are but four of us;

What can we possibly be?

Would you know more of us?

Twelve are but six of us,

Five are but four, do you see?

What are we?

They came out at night, without being called.
They lost at day, without being stolen.
Who are they?

During which month do people sleep the least?

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

Can you write down eight eights so that they add up to one thousand?

How many times can you subtract the number 5 from 25?

John was piloting a plane behind a car but was never able to overtake it. Why?

How many sides does a circle have?