Question

in each of the following number , replace (*) by the smallest number to make it divisible by 11., 6*809 , 516*74 , 7*125 .

Answer 1

As numbers as divisible by 11, when the sum of the numbers at the odd place of a number 'minus' the sum of the numbers at the even place of the number is  either 11 or 0 or a multiple of 11...therefore, 
6*809 = 23 - * = 22 (closest multiple of 11)
          = 1 
         = 61809
and using this method
516*74 = 516274
7*125 = 70125