Question

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

Answer 1

\(\Huge{welcome~to~openstudy}\)

Answer 2

how many favorable outcomes are possible?

Answer 3

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

Answer 4

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

Answer 5

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

Answer 6

which is why the formula we have is defied as:

P(AorB) = P(A) + P(B) - P(AandB)