How I look at it is that since the number of throws is lesser, there is lesser chance of all numbers coming up. Hence, 4 has a chance of coming up more than 1/4 times in two throws.

Another way to look at it is that in two throws only two numbers can come up and the chance of 4 coming up once in two trials will be higher than 1/6

4 not 4

not 4 4

1/6*5/6+5/6*1/6 = 25/36>1/4

sagarsingh wrote:

Cornelius wrote:

Let n be the number of times the dice is rolled to ensure that the probability of a 4 is at least 1/4.

Thus,

n*(probability of rolling a 4 in one turn)>= 1/4

n*(1/6)>= 1/4

n>6/4---->n>= 1.5

Hence "minimum number of times to ensure that the probability that a 4 is rolled is at least 1/4" >= 1.5 = 2 (since we cannot have 1.5 rolls)

Ans B

By this logic, in 6 throws, you have a probability of getting 4 as 1. I doubt if your approach is correct.

And in 7 and above throws the probability to get 4 will be more than 1. I dont know if I am missing something

_________________

Thanks

Kris

Instructor at Aspire4GMAT

Visit us at http://www.aspire4gmat.com

Post your queries

Join our free GMAT course

New blog: How to get that 700+

New blog: Data Sufficiency Tricks

Press Kudos if this helps!