# Math Help - K-Sided Dice

1. ## K-Sided Dice

Hi everyone,

Looking for a bit of help. If i throw a k-sided dice twice, what is the expected value of their sums. I'm looking for a formula for it including k.

Thanks

2. Originally Posted by waxandshine
Hi everyone,

Looking for a bit of help. If i throw a k-sided dice twice, what is the expected value of their sums. I'm looking for a formula for it including k.

Thanks
The expected value of the sum of two RV's is the sum of their expected values.

So what is the expected value of a single throw of a k-sided die.

CB

3. well yeah, but there's no values so it's basically the expected value of one roll times two, but i dont know hot to write a formula for the expected value of one roll

4. Originally Posted by waxandshine
well yeah, but there's no values so it's basically the expected value of one roll times two, but i dont know hot to write a formula for the expected value of one roll
Fair die so probability of each face is 1/k.

So expected value is:

$
(1)(1/k)+(2)(1/k)+..+(k)(1/k)=(1/k)\sum_{i=1}^k i
$

CB