If 100^25-25 is written in decimal notation, what is the sum of digits?

Warren,

Try some smaller exponents.
What is 100^{2} - 25? What is the sum of its digits?
What is 100^{3} - 25? What is the sum of its digits?
What about 100^{25} - 25?

Penny

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