If you roll two dice, what's the probability of rolling a seven (the numbers on the dice add up to 7 ) on or before the eighth roll?
A. 47
B. 767
C. 045
D. 049
E. 083
C. 045
Explanation: There are a total of 36 possible outcomes when rolling two dice. Out of those 36 outcomes, there are 6 ways to roll a seven (1+6, 2+5, 3+4, 4+3, 5+2, 6+1).
To find the probability of rolling a seven on or before the eighth roll, you need to find the complement - the probability of not rolling a seven in the first 7 rolls.
The probability of not rolling a seven in one roll is 30/36, or 5/6. Therefore, the probability of not rolling a seven in the first 7 rolls is (5/6)^7.
The probability of rolling a seven on or before the eighth roll is 1 - (5/6)^7 = 0.45 or 45%.
So the answer is 045.