If P(A|B) < P(A), then which one of the following is correct?

When the measure of central tendency is available in the form of mean, which one of the following is the most reliable and accurate measure of variability?

A problem is given to three students A, B and C, whose probabilities of solving the problem independently are $\rm \frac{1}{2}$, $\rm \frac{3}{4}$ and p respectively. If the probability that the problem can be solved is $\rm \frac{29}{32}$, then what is the value of p?

In a cricket match, a batsman hits a six 8 times out of 60 balls he plays. What is the probability that on a ball played he does not hit a six?