Spot 5 differences in two Christmas tree below:

In a mathematical quiz, you are asked the following question:

Use three 9s in a mathematical expression without dividing or multiplying to form the number one.

Can you answer the question?

What is more useful when it is broken?

You may enter, but you may not come in. I have space, but no room. I have keys, but open no lock. What am I?

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?

I speak without a mouth, and hear without ears. I have no-body, but I come alive with the wind. What am I?

What's the only room from which no one can enter or leave

An ant is travelling on a 1-meter-long rope at 1 cm/second but also the entire rope is being stretched by an extra 1 meter/second. Is it possible for the ant to reach at the end of the rope?

Find the missing number in the series below

13 -21 34 -55 ? -144

I come in different shapes and sizes.
Parts of me are curved, other parts are straight.
You can put me anywhere you like,
but there is only one right place for me.
What am I?