Vampires biting puzzle

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A vampire enters a town and bites 2 person every night. The bitten 2 persons grows in to two big vampires and bites 4 persons the next night. These 4 vampires bites 6 people the next night and the 6 bites 8 and so on…….

How many vampires will be there on the 5th night?

SherlockHolmes Expert Asked on 17th June 2016 in

Answer-71( assuming the bitten people don’t bite a larger group every next night)

Explanation:
No of people bitten

1st night       2nd night     3rd night     4th night      5th  night

The first vampire         –              2                         2                        2                      2                 2                   – 10

The Two new vampires
bite 4 persons
the next night                –              nil                       4                      4                     4                      4                -16
The Four new vampires
bite 6 persons
the next night                –             nil                    nil                      6                          6                   6                 -18
The Six new vampires
bite 8 persons
the next night                   –             nil                  nil                        nil                      8                    8              -16
The Eight new vampires
bite 10 persons
the next night                  –             nil                  nil                      nil                        nil               10                -10
Total            -70
The answer is 71 including the first vampire

Wedge Scholar Answered on 17th June 2016.

No of Vampires in First night                                      1
No of Persons Bitten in first Night                           2

No of Vampires in Second Night                               1+2 =3
No of Persons Bitten in Second Night                    2+4 =6

No of vampires In Third Night                                    1+2+2+4 =9
No of Persons bitten in Third Night                         2+4+4+6 =16

No of Vampires in Fourth Night                                 1+2+2+4+2+4+4+6=25
No of Persons bitten in Forth Night                         2+4+4+6+4+6+6+8=40

No of Vampires in Fifth Night                                      1+2+2+4+2+4+4+6+2+4+4+6+4+6+6+8=65
No of  persons bitten in Fifth night is                      2+4+4+6+4+6+6+8+4+6+6+8+6+8+8+10 = 96

So the Number of Vampires in Fifth Night is 65

dyj Expert Answered on 17th June 2016.

71

Durgesh Gupta Curious Answered on 18th June 2016.

38

Anish_Russel Starter Answered on 17th July 2016.

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