The sum of the series Sigma Sm is defined by 1^4+2^4+3^4+.............+n^4
where n=29 then value of Sm=???? today asked in Elitmus guys
A.0 B.1 C.3 D.4

• Answer would be 9, in qtn they asked about unit digit of Sm
  units digits of 1^4 is 1,2^4 is 6,3^4 is 1,4^4 is 6, 5^4 is 5, 6^4 is 6,7^4 is 1, 8^4 is 6, 9^4 is 1, 10^4 is always 0
  so up to 29 each unit digit repeats 3 times
  Hense unit digit in Sm is 3(1+6+1+6+5+6+1+6+1) =3(33) ......results unit digit 9.
• 10 years agoHelpfull: Yes(15) No(0)
• This question consumes a little bit of time as we have to understand the pattern of power fours.
  
  1 power four ends with 1
  2 power four ends with 6
  3 power four ends with 1
  4 power four ends with 6
  5 power four ends with 5
  6 power four ends with 6
  7 power four ends with 1
  8 power four ends with 6
  9 power four ends with 1
  
  Sum of all the units digits of power fours of first nine numbers is 33 or it ends with 3.
  
  For 10, power four ends with 0.
  
  For 11 to 19, the last digits of power fours again follow the same pattern and the sum of all of them will be 33 again.
  
  For 20, power four ends with 0.
  
  For 21 to 29, the last digits of power fours again follow the same pattern and the sum of all of them will be 33 again.
  
  The last digit depends on the sum of the last digits of all the numbers, so the last digit depends on 33 + 33 + 33 = 99.
  
  The unit’s digit of the entire sum will be 9.
  
  9 is the answer.
  
• 10 years agoHelpfull: Yes(8) No(0)
• in qus asked last digit of sm ok................................and in option 9 there .................ans 9 is correct ans
  
• 10 years agoHelpfull: Yes(5) No(4)
• questions asked first digit of nth term, where n=29.
  Ans will be 9*9*9*9= 6561 so ans= 1 option b
• 10 years agoHelpfull: Yes(2) No(4)
• 3. 1*4+...29*4
• 10 years agoHelpfull: Yes(0) No(0)
• what is the ans??
• 10 years agoHelpfull: Yes(0) No(0)