Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Probability

Question:

A natural number ‘n’ is selected at random from the set of first 100 natural numbers. The probability that $n+\frac{100}{n}≤50$ is equal to

Options:

$\frac{9}{10}$

$\frac{39}{50}$

$\frac{9}{20}$

None of these

Correct Answer:

$\frac{9}{20}$

Explanation:

$n+\frac{100}{n} \leq 50 $

$\Rightarrow n^2-50 n+100 \leq 0$

$\Rightarrow 25-5 \sqrt{21} \leq n \leq 25+5 \sqrt{21}$

⇒ n = 3, 4, 5...., 47

Thus, favourable number of ways

= (47 – 3 + 1) = 45

Thus, required probability = $\frac{45}{100}=\frac{9}{20}$