How many sides does a circle have?

Find the Next Number in the Sequence

2 9 3 1 8 4 3 6 5 7 ?

There is a circular car race track of 10km. There are two cars, Car A and Car B. And they are at the exact opposite end to each other. At Time T(0), Both cars move toward each other at a constant speed of 100 m/seconds. As we know both cars are at the same speed they will always be the exact opposite to each other.
Note, at the center, there is a bug which starts flying towards Car A at time T(0). When the bug reaches car B, it turns back and starts moving towards the car A. The speed of bug is 1m/second. After 5 hours all three stop moving.
What is the total distance covered by the bug?

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.

I possess a head

I flaunt a tail

But I don't have mouth or legs

Can you find out who I am?

Find out the missing number in the picture attached:

This is a classy optical illusion puzzle. What more you can find except bricks in the image below?

Can you find the key in the picture below?

A certain street contains 100 buildings. They are numbered from 1 to 100. How many 9's are used in these numbers?

Can you count the number of matches in the picture below ?