Baseball bat and ball cost $100. If the bat cost $99 more than the ball, what is the cost of each?

No matter how little or how much you use me, you change me every month. What am I?

After teaching his class all about Roman numerals (X = 10, IX=9 and so on) the teacher asked his class to draw a single continuous line and turn IX into 6. The teacher's only stipulation was that the pen could not be lifted from the paper until the line was complete.

Two batsman each on 94 runs. Seven runs needed to win in last 3 balls. Both make 100*. How?

Complete the table series riddle by finding the number that can replace "??".

The host of a game show, offers the guest a choice of three doors. Behind one is a expensive car, but behind the other two are goats.
After you have chosen one door, he reveals one of the other two doors behind which is a goat (he wouldn't reveal a car).

Now he gives you the chance to switch to the other unrevealed door or stay at your initial choice. You will then get what is behind that door.

You cannot hear the goats from behind the doors, or in any way know which door has the prize.

Should you stay, or switch, or doesn't it matter?

What does it mean?

I am the one who remains awake when you sleep. But I need to rest when you awake. Who Am I?

What is the fewest number of coins that would be required in order to make sure each and every coin touches exactly three other coins?

What is the next number in this series?

4,12,84,3612....