document.write( "Question 53621: I am having a hard time figuring out this problem.\r
\n" ); document.write( "\n" ); document.write( "Use the geometric sequence of numbers 1, 1/2, 1/4, 1/8,…to find the following:
\n" ); document.write( "a) What is r, the ratio between 2 consecutive terms? \r
\n" ); document.write( "\n" ); document.write( "b) Using the formula for the sum of the first n terms of a geometric series, what is the sum of the first 10 terms? Please round your answer to 4 decimals.
\n" ); document.write( "c) Using the formula for the sum of the first n terms of a geometric series, what is the sum of the first 12 terms? Please round your answer to 4 decimals.\r
\n" ); document.write( "\n" ); document.write( "Thanks for your help!
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Algebra.Com's Answer #35883 by funmath(2933)\"\" \"About 
You can put this solution on YOUR website!
Geometric Sequence: {1,1/2,1/4,1/8...}
\n" ); document.write( "a)r=a(sub n+1)/a(sub n) in some books r=a(sub n)/a(sub n-1). It's the same thing, divide the 2nd term by the 1st, the 3rd by the 2nd, ect.
\n" ); document.write( "r=(1/2)/(1)=1/2
\n" ); document.write( "---
\n" ); document.write( "r=(1/4)/(1/2)
\n" ); document.write( "r=(1/4)*(2/1)
\n" ); document.write( "r=2/4=1/2
\n" ); document.write( "---
\n" ); document.write( "r=(1/8)/(1/4)
\n" ); document.write( "r=(1/8)*(4/1)
\n" ); document.write( "r=4/8=1/2
\n" ); document.write( "---
\n" ); document.write( "Notice that in geometric sequences, you will get the same ratio with any two consecutive terms, in this case:r=1/2.
\n" ); document.write( "-------------------------------------------------------------------------------
\n" ); document.write( "b)The sum of the first n terms is:
\n" ); document.write( "\"S%28sub+n%29=a%28sub+1%29%2A%281-r%5En%29%2F%281-r%29\"
\n" ); document.write( "In this case you want the sum of the first 10 terms.
\n" ); document.write( "n=10
\n" ); document.write( "r=1/2
\n" ); document.write( "The first term, a(sub 1)=1
\n" ); document.write( "\"S%28sub+10%29=1%2A%281-%281%2F2%29%5E10%29%2F%281-1%2F2%29\"
\n" ); document.write( "\"S%28sub+10%29=%281-1%2F1024%29%2F%281-1%2F2%29\"
\n" ); document.write( "\"S%28sub+10%29=%281024%2F1024-1%2F1024%29%2F%282%2F2-1%2F2%29\"
\n" ); document.write( "\"S%28sub+10%29=%281023%2F1024%29%2F%281%2F2%29\"
\n" ); document.write( "\"S%28sub+10%29=%281023%2F1024%29%2A%282%2F1%29\"
\n" ); document.write( "\"S%28sub+10%29=1023%2F512\"
\n" ); document.write( "S(sub 10)=1.9980
\n" ); document.write( "-------------------------------------------------------------------------------
\n" ); document.write( "c) This time
\n" ); document.write( "n=12
\n" ); document.write( "r=1/2
\n" ); document.write( "a(sub 1)=1
\n" ); document.write( "\"S%28sub+n%29=a%28sub+1%29%2A%281-r%5En%29%2F%281-r%29\"
\n" ); document.write( "\"S%28sub+12%29=1%2A%281-%281%2F2%29%5E12%29%2F%281-1%2F2%29\"
\n" ); document.write( "\"S%28sub+12%29=%281-1%2F4096%29%2F%281-1%2F2%29\"
\n" ); document.write( "\"S%28sub+12%29=%284096%2F4096-1%2F4096%29%2F%282%2F2-1%2F2%29\"
\n" ); document.write( "\"S%28sub+12%29=%284095%2F4096%29%2F%281%2F2%29\"
\n" ); document.write( "\"S%28sub+12%29=%284095%2F4096%29%2A%282%2F1%29\"
\n" ); document.write( "\"S%28sub+12%29=4095%2F2048\"
\n" ); document.write( "S(sub 12)=1.9995
\n" ); document.write( "Happy Calculating!
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