if 7^21+7^22+7^23+7^24=N,then what is the remainder when N is divided by 25?

• remainder = 0.. as 7^21+7^22+7^23+7^24 will have 00 at its tens and ones place respectively.
• 12 years agoHelpfull: Yes(14) No(1)
• answer is zero
  7^21(1+7+7^2+7^3)
  =(7^3)7(400)
  =(343)^7(400)
  =3*400=1200.
• 12 years agoHelpfull: Yes(10) No(1)
• since the result of N=7^21+7^22+7^23+7^24=223418345633313602800
  clearly we have 0 at the unit place and 0 at the tens place as well,
  so, by the number system , N is perfectly divisible by 25
  so, remainder of N%25 is 0
  Ans-> 0(zero)
• 12 years agoHelpfull: Yes(3) No(0)
• 7^21(1+7+49+343)=(7^21*400)/25
  remainder is zero
• 12 years agoHelpfull: Yes(2) No(0)
• 12 is the remainder
• 12 years agoHelpfull: Yes(1) No(6)
• 7^21(1+7^1+7^2+7^3)
  = 7^21(1+7+49+343)
  =7^21(400)
  now here , if we divide 7^21(400)by 25
  Then 400 will be divided by 25 and as 400 is multiplied to 7^21
  therefore the whole term is completely divided by 25
  Thus remainder is 0.
• 7 years agoHelpfull: Yes(1) No(0)
• the last 2digit of this sum is 70
  so when divided by 25 reminder will be 20.
• 12 years agoHelpfull: Yes(0) No(4)
• 4 remainder
• 12 years agoHelpfull: Yes(0) No(3)
• Lat 2 digit of the sum is 00.
  So,remainder is 0
• 12 years agoHelpfull: Yes(0) No(0)
• 0 is right answer
  
• 12 years agoHelpfull: Yes(0) No(0)
• @saurabh
  please explain
• 12 years agoHelpfull: Yes(0) No(0)
• can any one tell me the process to find out last digits of a product
• 12 years agoHelpfull: Yes(0) No(0)
• 7/25 + 24/25 + 18/25 + 1/25= remainder is 0
• 7 years agoHelpfull: Yes(0) No(0)