Elitmus
Exam
Numerical Ability
Permutation and Combination
How many 5 digit number can be formed out of digits 0,2,4,6,8 that is divisible by 8.
1. 26 2. 30
3. 38 4. 96
Read Solution (Total 7)
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- For a number to be divisible by 8, its last three digits must divisible by 8.
So, last three digits can be from the following group
(024), (048), (064), (208), (240), (248), (264), (280), (408), (480), (608), (624), (640), (648), (680), (824), (840), (864),
There are 18 such groups.
Consider these 12 groups in which zero is there
(024), (048), (064), (208), (240), (280), (408), (480), (608), (640), (680), (840)
With each of these 12 groups, first digit can be any of the remaining 2 digits and second digit can be the remaining one digit
Therefore, 12×2 = 24 such numbers
Consider the 6 groups in which zero does not come
(248), (264), (624), (648), (824), (864),
With each of these 6 groups, first digit can be the one remaining digit(because zero cannot be the first digit)
Second digit can be zero
Therefore, 6×1 = 6 such numbers
Therefore, total count of 5 digit numbers = 24 + 6 = 30
So, Ans is 30 - 8 years agoHelpfull: Yes(59) No(2)
- 2. 30 is the ans .
there is a procedure to solve such kind of problem checkout this link
http://www.careerbless.com/qna/discuss.php?questionid=1493 - 8 years agoHelpfull: Yes(11) No(1)
- 0 can not be at first place so choices for first place is 4
For second place it is also 4 because one digit is already selected
Divisibility rule of 8 is last three digit should be divisible by 8 here it is 6
So 4*4*6=96
Ans is 4. 96
- 8 years agoHelpfull: Yes(2) No(25)
- B....has been crying...
- 8 years agoHelpfull: Yes(2) No(7)
- Don't know
- 7 years agoHelpfull: Yes(0) No(3)
- i could be 96
- 7 years agoHelpfull: Yes(0) No(1)
- 96 is the ans
- 5 years agoHelpfull: Yes(0) No(1)
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