Latest MBA Aptitude Question SOLUTION: How many 5 digit numbers exist having exactly two 4s in them?

1) 6804
2) 5427
3) 3888
4) 1377

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(#M40014813) MBA HR Interview question permutations and combinations, probability Keep an EYE

How many 5 digit numbers exist having exactly two 4s in them?

1) 6804
2) 5427
3) 3888
4) 1377

Asked In MBA (11 years ago)

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SRIRAMKUMAR  (9 years ago)

the five digit number can be represented as xxxx out of these 4s can appear in any two positions
zero cant appear in first position so when 4 does not occupy first position ,it can occupy any other four positions.the number of posibilities is=4C2*8*9*1*1=3888
when 4 appears in the first position four occupy any of the other four positions.
the number of posibilities is 4C1*9*9*9*1=2916
total numbers=2916+3888=6804

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radhika  (7 years ago)

1)6804
1st case
first digit from left is 4
so 4c1*9*9*9
we know that first palace is 4
we choose a palace 4c1 and fixed it by 4
4*9*9*9=2916
2nd case
first digit from left is not 4
so 4c2*8*9*9=6*8*9*9=3888
so total numbers =2916+3888=6804
6804 is right answer

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