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(#M40155013) ELITMUS Numerical Ability question APTITUDE Keep an EYE

How many perfect numbers are there in combination of numbers made by using 4 digits.

Asked In Elitmus Tikendra (9 years ago)

Unsolved Read Solution (8)

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Read Solution (8) :

rituraj  (9 years ago)

Answer is = 1 and that is 8128.
They are asking about perfect numbers not perfect squares.
Perfect Numbers are those numbers which are equal to (sum of all its factors/2).
Like
( 1 + 2 + 3 + 6 ) / 2 = 6.
The next perfect number is 28 = 1 + 2 + 4 + 7 + 14.
This is followed by the perfect numbers 496 and 8128.

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NAVEEN KUMAR  (9 years ago)

https://en.wikipedia.org/wiki/List_of_perfect_numbers

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Sajid Ahsan  (9 years ago)

formulae to findout Perfect Nunmber is:
2p−1(2p − 1) where p is prime number
for p = 2: 21(22 − 1) = 6

for p = 3: 22(23 − 1) = 28

for p = 5: 24(25 − 1) = 496

for p = 7: 26(27 − 1) = 8128.

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sandeep devalla  (9 years ago)

Sorry to say this i think your answer is wrong, answer is 1 because they asked for perfect number but not perfect square number, so for finding perfect number formula is (2^(p-1))((2^p)-1) for p=1,2,3, so on.

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SOUMYADIP MITRA  (9 years ago)

the first 4 digit perfect square number is 1024=32*32 and ends with
99*99=9801
so the total possibilities =68

Is this solution Helpfull? Yes (2) | No (4)  

mitansh kanojiya  (9 years ago)

(2^(p-1))((2^p)-1) this is the formula for even perfect number
so the answer if we put 4 in the place of p then answer is 120

Is this solution Helpfull? Yes (2) | No (1)  

mamta kumari  (9 years ago)

hii frndz...i didnt write elitmus .so dont know exactly what questions do they ask in data interpretation means related to which charts table charts pie charts bar charts or line charts...plz do help me yarr..

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Giri  (9 years ago)

perfect number is when we add the factors of that number excluding the number(number itself) then the number equals to that number eg: 6 is perfect number factors of 6 is 1,2,3,6 but we have to exclude 6 then the sum of remaining number is 1+2+3=6 and 28 is perfect number factors are 1,2,14,7,4,28 we have to exclude 28 then sum is 1+2+14+7+4=28 so the perfect number formed by four digit number is 8128

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