Consider a two digit number x and and another number y with x's digits reversed which of the following cannot be x+y, indicate all that apply?
option
a) 121
b) 220
c) 111
d) 110
e) 187

• ANS: 111
  Let x be 10a+b
  Then digits reversed will produce y= 10b+a
  So sum of these two numbers=x+y= 11a+11b=11(a+b)
  So the new number formed must be divisible by 11
  Among the given numbers, 111 is the only one which is not divisible by 11 hence, it cannot be x+y
  
• 11 years agoHelpfull: Yes(8) No(0)
• 111
  If a & b are the digits of tens & unit place respectively,then
  First number,x=10a+b and y=10b+a
  So x+y=(10a+b)+(10b+a)=11(a+b)
  So number multiple of 11 can be a sum of x & y, except 111
  
• 11 years agoHelpfull: Yes(3) No(0)
• @Rahul your answer is right but we got an exceptional condition.
  since the maximum 2 digit number is 99 and after interchanging the digits we get 99 itself.by adding these two we get 198 as sum.So along with 111,220 also be the answer.
  220=11*20=11*(11+9).
  But according to the logic a and b must be single digit numbers.
  
• 11 years agoHelpfull: Yes(1) No(0)