if
25 = 15
36 = 24
49 = 31
64 = 52
then what can be value of 81 in this system.

• I think it ll be 65
  
  25 = 15
  25 - (2+5) + (2-5) = 15
  36 = 24
  36 - (3+6) + (3-6) = 24
  49 = 31
  49 - (4+9) + (4-9) = 31
  64 = 52
  64 - (6+4) + (4-6) = 52 [Subtract the larger digit from the smaller digit]
  
  Similarly
  81 - (8+1) + (1-8) = 65
  
  Ans : 65
  
  
• 10 years agoHelpfull: Yes(12) No(1)
• 65
  
  25 ---> 25 - 2*5 = 25-10 = 15[number - 2*larger digit]
  36 ---> 36 - 2*6 = 36-12 = 24
  49 ---> 49 - 2*9 = 49-18 = 31
  64 ---> 64 - 2*6 = 64-12 = 52
  81 ---> 81 - 2*8 = 81-16 = 65
  
• 10 years agoHelpfull: Yes(3) No(0)
• 25 = 15
  25 - (2+5) + (2-5) = 15
  36 = 24
  36 - (3+6) + (3-6) = 24
  similarly add & subtract the digits to the number.
  Hence ans is 65
  
• 10 years agoHelpfull: Yes(0) No(0)
• the answer is 79 because right side first digit 1 mean left side 2, 2 mean 3, etc so 7 for 8.Then in third point 9 for 1
• 9 years agoHelpfull: Yes(0) No(0)