Probability Practice Test 1

Question : 21 of 40

Marks: +1, -0

A five-digit number is formed by using thedigits, 1, 2, 3, 4 and 5 without repetitions.What is the probability that the number isdivisible by 4?

$1/5$
$5/6$
$4/5$
None of these

Validate

Solution:

Given digits = 1, 2, 3, 4, 5
Total number formed by three digits = 5! = 120
A number will be divisible by 4 if the last two digit are divisible by 4.
∴ Last two digits can be 12, 24, 32, 52.
They can be filled in 4 ways.
These four ways are possible by 3! ways.
Hence, number of ways in which the number formed is divisible by 4 = 4 × 3! = 4 × 3 × 2 × 1 = 24
Required probability

=24/120=1/5

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