Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Probability

Question:

Three numbers are selected simultaneously from the set {1, 2, 3, …., 25}. The probability that the product of selected numbers is divisible by 4, is equal to

Options:

$\frac{1}{115}$

$\frac{98}{115}$

$\frac{773}{1150}$

$\frac{963}{1150}$

Correct Answer:

$\frac{773}{1150}$

Explanation:

Product can’t be divisibly by 4 in the following mutually exclusive cases;

(i) All the selected numbers are odd.

corresponding ways = ${ }^{13} C_3=286$

(ii) Two of the selected numbers are odd and another is a multiple of 2 only.

Corresponding ways = ${ }^{13} C_2 . { }^6 C_1=468$

Thus, required probability

$=1-\frac{(286+468)}{{ }^{25} C_3}=\frac{773}{1150}$