Use only one mathematical symbol and all numbers (0-9) to get a sum of 99

If an electric train is travelling south, then which way is the smoke going?

I have lakes with no water, mountains with no stone and cities with no buildings. What am I?

Find the next number in the sequence

1, 2, 6, 21, 88, __?

Why is it against the law for a man living in Delhi to be buried in Mumbai?

Can you tell a 3D object that has just two surfaces?

On her drawing table, Sayna lit 12 coloured candles. A few seconds later she blew two candles off.

How many candles Sayna have at the end?

Can you find out a way through which you can make five squares out of the given figure by moving just six match sticks?

You walk into a creepy house by yourself. There is no electricity, plumbing, or ventilation. Inside you notice 3 doors with numbers on them. Once you open the doors you will die a particular way. Door No.1 You’ll be eaten by a lion who is hungry. Door No.2 You’ll be stabbed to death. Door No.3 There is an electric chair waiting for you. Which door do you pick?

John and Jacob are twin brothers. One of them is a liar whereas the other one is a truth-teller.

I called their home number and one of them picked up.
I asked. 'Does John lie?' The person replied with a yes.

Whom did I talk with, John or Jacob?