Taikiqi
CrackVerbalGMAT
Probability of getting a 6 on the first throw or the second throw or both is equivalent to saying getting at least 1 six in 2 throws = 1 - P(not getting a six in either throw)
P(getting a six) = 1/6, therefore P(not getting a six) = 5/6
Required probability = 1 - (5/6 * 5/6) = 1 - 25/36 = 11/36
Option D
Arun Kumar
Good evening Kumar,
Thank you for your explanation. Can you please help me understand why my answer is not right?
I use the the chance to have first “6” plus the chance to have second “6” plus the chance to have both “6”.
1/6 + 1/6 + (1/6 x 1/6) = 13/36......
Can you please help?
Thanks.
Posted from my mobile deviceHello Taikiqi. You are rolling a dice twice. So if you are getting a 6 on the first throw who's probability is 1/6, then you are not getting a 6 in the 2nd throw. This probability is 5/6. Therefore the combined probability for this event is 1/6 * 5/6 = 5/36
Similarly, when you get a 6 in the 2nd throw, but not on the 1st, then the probability of this event is also 5/6 * 1/6 = 5/36.
When you get a 6 in both throws, as you have done it, it's 1/6 * 1/6 = 1/36
Overall probability = 5/36 + 5/36 + 1/36 = 11/36
Hope this helps.
Arun Kumar