TS ICET 23 May 2018 Shift 2 Paper

Question : 150 of 200

Marks: +1, -0

If a four digit number is formed at random using the digits 2. 5. 7. 8. 9 then the probability that the sum of the digits in that number is a multiple of 2 is

$2/5$
$3/5$
$3/10$
$7/10$

Validate

Solution:

The number of four digit numbers formed is

^5P_4= 120.

The number of four digit numbers formed whose sum of the digits divisible by 2 is same as the number formed by two even digits and two odd digits.
Favourable cases

{=^{2} C _{2} ×^{3} C _{2} × 4 !

∴ Required Probability

=\;{3 × 4 !}/{5 !}=\;{3}/{5}

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