Mathematics - Probability Question with Solution | TestHub

MathematicsProbabilityGeneral (Event SS, Definitions, Odd against/Favour)Hard2 minPYQ_2021

MathematicsHardsingle choice

Let $A$ be a set of all $4$ -digit natural numbers whose exactly one digit is $7$ . Then the probability that a randomly chosen element of $A$ leaves remainder $2$ when divided by $5$ is:

Options:

Answer:

Solution:

$n (s) = n$ ( when $7$ appears on thousands place ) $+ n$ ( $7$ does not appear on thousands place)

$= 9 \times 9 \times 9 + 8 \times 9 \times 9 \times 3$

$= 33 \times 9 \times 9$

$n (E) = n$ ( last digit $7 & 7$ appears once) $+ n$ ( last digit $2$ when $7$ appears once)

$= 8 \times 9 \times 9 + (9 \times 9 + 8 \times 9 \times 2)$

$∴ P (E) = \frac{8 \times 9 \times 9 + 9 \times 25}{33 \times 9 \times 9} = \frac{97}{297}$

Stream:JEESubject:MathematicsTopic:ProbabilitySubtopic:General (Event SS, Definitions, Odd against/Favour)

⏱ 2mℹ️ Source: PYQ_2021

Doubts & Discussion

Loading discussions...