SEARCH HOME
 Math Central Quandaries & Queries
 Question from SHIVDEEP, a student: The sum of digits of 4444^4444 is A .The sum of digits of A is B . Find the sum of digits of B ? Please help me solving this...

Shivdeep,

If you were to repeat the process of adding the digits of a number to a new number, you'd get the remainder of division of 44444444 by 9. For instance, 4444/9 = 493 remainder of 7. You can also compute the remainder by adding 4+4+4+4 = 16, 1+6 = 7.

Now 44444444 < 100004444, so 44444444 has at most 4 × 4444 = 17776 digits, each of which is at most 9. So A is at most 9 × 17776 = 159984. The number smaller than 159984 with the largest digit sum is 99999, and 9+9+9+9+9 = 45. So B is at most 45, and the sum of digits in B is at most 3 + 9 = 12.

You'll have to figure out what is the remainder of division of 44444444 by 9. If you are lucky, it is not 1, 2 or 3, so there is only one number from 1 to 12 which has the same sum of digits.

Claude

Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.