I new to dnd and I was looking at the stats of a monsters attack. It says that on a failed save the target takes 55 (10d10) damage. I don't understand whether the target takes ten d10 dice or do you actually multiply the two numbers and they take 550 d10 dice. I assume it is just ten d10 because 550 d10 seems crazy but I might be wrong.

The average roll of 10d10 is 55.   (5.5 is the average for 1d10, 5.5x10= 55)   The number 55 is what you are supposed to use if you hate dice.

Which is silly because if you hate dice, you do not play this game.  I know nobody that uses the average dice roll for damage.

Thank you for the clarification I found this confusing like who doesn't roll dice?!

In games with lots of players/monsters - it's much quicker to just take the average value and move on. You want to keep the game going and not take all week. Same can be said for running games with younger kids - you can just say their attacks do the average damage and then they don't have to do maths which might take all month.

Quote from mrsamiam787 >>

Thank you for the clarification I found this confusing like who doesn't roll dice?!

 
When you have a lot of monsters in an encounter rolling all the dice everytime takes a long time, especially if rolling physically and you have to stop to count them. In these situations many DMs may opt to use the average instead to speed things up so the players aren't waiting several minutes of monster turns when it could be just 1 or 2 if using averages.

EDIT: Ninja'd by Emmber.