Sum of digits of the number (192)^4 times (5)^21?  TOPIC_SOLVED

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Sum of digits of the number (192)^4 times (5)^21?

Postby Chasyesker on Thu Sep 26, 2013 11:39 pm

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?
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Re: Sum of digits of the number (192)^4 times (5)^21?  TOPIC_SOLVED

Postby little_dragon on Thu Sep 26, 2013 11:51 pm

Chasyesker wrote: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
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