Why do we preferably have round manhole covers and not square ones?

Can you find out the next digit in the following series ?

0, 0, 1, 3, 2, 6, 3, 9, 4, 12, 5, ?

If 1+9+8=1, what is 2+8+9?

Can you solve below mathematical equation?

2^1234 - 2^1233

Replace the letters of words with a number so that the below equation holds true

BASE +
BALL
---------
GAMES
----------

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

Four men were in a boat on the lake. The boat turns over, and all four men sink to the bottom of the lake, yet not a single man got wet! Why?

How can you make number one disappear by adding something to it?

Can you make numbers like 24, using numbers 3,3,7 & 7 with any arithmetic operator?

A swan sits at the center of a perfectly circular lake. At an edge of the lake stands a ravenous monster waiting to devour the swan. The monster can not enter the water, but it will run around the circumference of the lake to try to catch the swan as soon as it reaches the shore. The monster moves at 4 times the speed of the swan, and it will always move in the direction along the shore that brings it closer to the swan the quickest. Both the swan and the the monster can change directions in an instant.
The swan knows that if it can reach the lake's shore without the monster right on top of it, it can instantly escape into the surrounding forest.

How can the swan successfully escape?