Latest TCS Aptitude Question SOLUTION: HOW MANY NUMBERS ARE THERE FROM 1 TO 400 HAVING EXACTLY THREE INTEGRAL FACTORS?

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(#M40154956) TCS Numerical Ability question NUMBER SYSTEMS Keep an EYE

HOW MANY NUMBERS ARE THERE FROM 1 TO 400 HAVING EXACTLY THREE INTEGRAL FACTORS?

Asked In TCS N Murali Krishna (8 years ago)

Unsolved Read Solution (14)

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Read Solution (14) :

tany  (8 years ago)

@priyadharshini
there are total 8 nos. less than 400 having three integral factors
4 , 9 , 25 , 49 , 121 , 169 , 289 , 361

Is this solution Helpfull? Yes (29) | No (1)  

priyadharshini  (8 years ago)

square of prime numbers are divisible by 1, itself and prime no.. eg: factors of 4 are 4,2,1..
the no's are 4,9,25,49,81... 361 (19^2)
answer is 9..

Is this solution Helpfull? Yes (22) | No (8)  

GOWRABATHUNI RAJESH  (8 years ago)

i think 8 is the answer

Is this solution Helpfull? Yes (3) | No (2)  

Aparna kumari  (8 years ago)

In this case, Number of factors is 3 and two of the three factors of a number are 1 and the number itself. The third factor has to be a prime number.
so p+1=3
p=2
n=a2
a2=400
a=20
so prime values between 1 to 20 is 2,3,5,7,11,13,17,19 so answer is 8

Is this solution Helpfull? Yes (3) | No   

priyadharshini  (8 years ago)

@tany yup.. s.. the ans is 8
Thnx for ur correction!!

Is this solution Helpfull? Yes (2) | No   

sanjeev kumar  (8 years ago)

Ans is 8
square of prime number and 9 total 7+1=8

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

Deepesh Malviya  (8 years ago)

Square of prime no. always have exactly 3
Integral factors.

Is this solution Helpfull? Yes (2) | No   

Bushra  (8 years ago)

ans is 20.. as the question is how many no's have three factors..

Is this solution Helpfull? Yes (1) | No (4)  

shivam varshney  (8 years ago)

In this case, Number of factors is 3 and two of the three factors of a number are 1 and the number itself. The third factor has to be a prime number.

P+1 = 3 or p = 2

Therefore, N = a^2

N < 400

or a^2 < 400

or a < 20

Since P is a prime number, p can assume 10 values (Take every prime number between 1 and 20 viz. 2, 3, 5, 7, 11, 13, 17, 19)

Thus Ans = 8

Is this solution Helpfull? Yes (1) | No   

stalin  (8 years ago)

answer is 7..as its asked to find perfect cube number less 400

Is this solution Helpfull? Yes | No (5)  

prasanta mishra  (8 years ago)

Can u explain the solution As well as question .

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mukesh vooka  (8 years ago)

what about 171 guyz 171 having also only 3 integral factors

Is this solution Helpfull? Yes | No (3)  

SHIVAM SAHU  (8 years ago)

square of prime no. only have 3 integral factor
4,9,25,49,81,121,169,289,961
answer is:9

Is this solution Helpfull? Yes | No (4)  

Anshul jain  (8 years ago)

any one explain question

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