Question

A symmetrical die is rolled $720$ times. Getting a face with four points is considered to be a success. The mean and variance of the number of successes is

• A. $20,120$
• B. $120,100$
• C. $100,100$
• D. $50,50$

Answer 1

Answer: (B)

$120,100$

Here, $n=720,p=\frac{1}{6},q=\frac{5}{6}$
$\therefore$ mean $=np=120$ and variance $=npq=100$