What is the units digit in the standard decimal expansion of the number 7^25.
(A) 1
(B) 3
(C) 5
(D) 7
(E) 9

• ans is D.
  unit digits
  7^1=7
  7^2=9
  7^3=1
  7^4=7
  it is repeated as 7,9,1,so 7^25 units digit is 7
  
• 9 years agoHelpfull: Yes(4) No(5)
• 7^25 can be written as (7^4)^6 * 7
  the units digit of 7^4 is 1.
  (1)^6 * 7= 7
  so the units digit in the standard decimal expansion of the number 7^25 is 7.
  
• 9 years agoHelpfull: Yes(0) No(0)
• answer is:D
  in units place we get
  7^1=7
  7^2=9
  7^3=3
  7^4=1
  7^5=7
  every 5th time the units place is repeated .so,the 25th time the units place will be 7.
• 5 years agoHelpfull: Yes(0) No(0)