My son and I are stumped. Without using a calculator what is the sum of the digits of the number (192)^4 times (5)^21?
U do powers of 10:
192=3*64=3*2^6
192^4=(3*2^6)^4=3^4 * 2^24
192^4 * 5^21 = 3^4 * 2^24 * 5*21 = 3^4 * 2^3 * 2^21 * 5^21 = 3^4 * 2^3 * 10^21
10^21 just does 21 zeros so U can ignore it
that leaves 81*8 & U dont need a calc for that