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

• @priyadharshini
  there are total 8 nos. less than 400 having three integral factors
  4 , 9 , 25 , 49 , 121 , 169 , 289 , 361
• 9 years agoHelpfull: Yes(29) No(1)
• 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..
• 9 years agoHelpfull: Yes(22) No(8)
• i think 8 is the answer
• 9 years agoHelpfull: Yes(3) No(2)
• 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
  
• 9 years agoHelpfull: Yes(3) No(0)
• @tany yup.. s.. the ans is 8
  Thnx for ur correction!!
• 9 years agoHelpfull: Yes(2) No(0)
• Ans is 8
  square of prime number and 9 total 7+1=8
• 9 years agoHelpfull: Yes(2) No(1)
• Square of prime no. always have exactly 3
  Integral factors.
• 8 years agoHelpfull: Yes(2) No(0)
• ans is 20.. as the question is how many no's have three factors..
• 9 years agoHelpfull: Yes(1) No(4)
• 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
• 9 years agoHelpfull: Yes(1) No(0)
• answer is 7..as its asked to find perfect cube number less 400
  
• 9 years agoHelpfull: Yes(0) No(5)
• Can u explain the solution As well as question .
  
• 9 years agoHelpfull: Yes(0) No(0)
• what about 171 guyz 171 having also only 3 integral factors
  
• 9 years agoHelpfull: Yes(0) No(3)
• square of prime no. only have 3 integral factor
  4,9,25,49,81,121,169,289,961
  answer is:9
  
• 9 years agoHelpfull: Yes(0) No(4)
• any one explain question
• 9 years agoHelpfull: Yes(0) No(2)