Find the sum of the first 10 terms of the following sequence. Round to the nearest hundredth if necessary.27,18,12,…Sum of a finite geometric series:Sn=1−ra1−a1rnAnswer:
Q. Find the sum of the first 10 terms of the following sequence. Round to the nearest hundredth if necessary.27,18,12,…Sum of a finite geometric series:Sn=1−ra1−a1rnAnswer:
Identify sequence type: First, identify the type of sequence given. The sequence 27,18,12,… is a geometric sequence because each term is obtained by multiplying the previous term by a common ratio.
Determine first term: Determine the first term a1 of the sequence. The first term a1 is 27.
Find common ratio: Find the common ratio r of the sequence. To find the common ratio, divide the second term by the first term: r=2718=32.
Use sum formula: Use the formula for the sum of the first n terms of a geometric series: Sn=1−ra1−a1⋅rn. We need to find the sum of the first 10 terms, so n=10.
Plug values into formula: Plug the values into the formula: S10=(1−32)(27−27×(32)10).
Calculate sum: Calculate the sum: S10=3127−27×(32)10.
Simplify expression: Simplify the expression: S10=3127×(1−(32)10).
Calculate (32)10: Calculate (32)10: (32)10≈0.01734 (rounded to five decimal places).
Substitute value into formula: Substitute the value back into the sum formula: S10=27×(1−0.01734)/(1/3).
Perform multiplication and division: Simplify the expression: S10=27×(0.98266)/(31).
Calculate final sum: Perform the multiplication and division: S10=27×0.98266×3.
Round to nearest hundredth: Calculate the final sum: S10=79.54794.
Round to nearest hundredth: Calculate the final sum: S10=79.54794. Round to the nearest hundredth: S10≈79.55.
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