Question
A five digit number divisible by 3 has to be formed using the numerals 0, 1, 2, 3, 4 and 5 without repetition. The total number of ways in which this can be done is
Answer: Option A
:
A
We know that a five digit number is divisible by 3, if and only if sum of its digits (= 15) is divisible by 3, therefore we should not use 0 or 3 while forming the five digit numbers.
Now,
(i) In case we do not use 0 the five digit number can be formed (from the digit 1, 2, 3, 4, 5) in 5P5ways.
(ii) In case we do not use 3, the five digit number can be formed (from the digit 0, 1, 2, 4, 5) in 5P5−4P4= 5! - 4!= 120 - 24 = 96 ways.
(4P4= cases when 0 is at the first position)
∴The total number of such 5 digit number = 5P5+(5P5−4P4)=120+96=216
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:
A
We know that a five digit number is divisible by 3, if and only if sum of its digits (= 15) is divisible by 3, therefore we should not use 0 or 3 while forming the five digit numbers.
Now,
(i) In case we do not use 0 the five digit number can be formed (from the digit 1, 2, 3, 4, 5) in 5P5ways.
(ii) In case we do not use 3, the five digit number can be formed (from the digit 0, 1, 2, 4, 5) in 5P5−4P4= 5! - 4!= 120 - 24 = 96 ways.
(4P4= cases when 0 is at the first position)
∴The total number of such 5 digit number = 5P5+(5P5−4P4)=120+96=216
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