By using 1,2,3,4,5,how many 5 digit no. Can be formed which is divisible by 4,repe-tation of no. Is allowed?

5

5 Answers

Oddman Profile
Oddman answered
For divisibility by 4, the number must end in one of these digit pairs
  12, 32, 52, 24, 44
The remaining 3 digits may have any of 5^3 = 125 values.
  125*5 = 625 such numbers can be formed.
Anonymous Profile
Anonymous answered

All of you have answered this question wrongly...
Since the number has to be divisible by 4 we can have only the following cases
12,24,32,44,52.That is you can fill the last two blanks in 5 ways

So in the first case the first digit can have 5 values....2nd digit can have 5 values....3rd digit can have 5 values....so for Iast case----5*5*5=125

for 5 such cases....125*5=625...
But there are 5 cases so 625*5=3125

Maynard Keynes Profile
Maynard Keynes answered
You should put the 2,4 at the last. And you divisible the numbers by 2, you should let the number be divisibled by 2.
Anonymous Profile
Anonymous answered
The answer is 24.
Well here is the solution:-Take 5 blanks _ _ _ _ _.
Since the number has to be divisible by 4 we can have only the following cases
12,24,32,52.That is you can fill the last two blanks in 4 ways.
Now take the first three blanks.Since we already selected 2 numbers,we are left with 3 numbers.
That is we can fill the first blank in 3 ways,similarly the second in 2,the third in 1 way.
By fundamental principle of counting we have to multiply all of them.
That is 3 x 2 x 4=24.

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