Imagine rolling two standard six-side dice. What is the P(two even or doubles)

Question

Imagine rolling two standard six-side dice.  What is the P(two even or doubles)

anonymous · Answer

$\Huge{welcome~to~openstudy}$

amistre64 · Answer

how many favorable outcomes are possible?

amistre64 · Answer

if the two at once is confusing, imagine it as rolling the dice twice

amistre64 · Answer

P(even) is, well there are 3 evens out of 6 sides:  1/2

if we roll an even and and even, P(even and even) = 1/2 * 1/2

amistre64 · Answer

and since each side has 1/6 of a chance of showing, the probability of rolling the same number twice is:  1/6 * 1/6

but heres a catch,  weve already counted some of the doubles:  2,2  4,4  6,6, theres 3 of them

amistre64 · Answer

which is why the formula we have is defied as:

P(AorB) = P(A) + P(B) - P(AandB)