document.write( "Question 1201932: s= 3 + 3 ^ 2 + 3 ^ 3 +***+3^ z
\n" ); document.write( "If s is the sum of the series given above, for which of the following values of n will s be divisible by 10? \n" ); document.write( "

Algebra.Com's Answer #836529 by greenestamps(13200) $\"\"$ $\"About$

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\n" ); document.write( "s= 3 + 3 ^ 2 + 3 ^ 3 +...+3^ z
\n" ); document.write( "If s is the sum of the series given above, for which of the following values of $\"cross%28n%29\"$ z will s be divisible by 10?

\n" ); document.write( "The sum is divisible by 10 if the units digit of the sum is 0.

\n" ); document.write( "z=1: units digit of the sum is 3
\n" ); document.write( "z=2: units digit of the sum is 3+9 = 12 --> 2
\n" ); document.write( "z=3: units digit of the sum is 3+9+7 = 19 --> 9
\n" ); document.write( "z=4: units digit of the sum is 3+9+7+1 = 20 --> 0

\n" ); document.write( "The units digits of the sums for larger values of z will follow the same pattern, so the units digit of the sum will be 0 for any value of z that is a multiple of 4.

\n" ); document.write( "ANSWER: any multiple of 4

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