Find the sum of the first 9 terms of the following sequence. Round to the nearest hundredth if necessary.75,66,58.08,…Sum of a finite geometric series:Sn=1−ra1−a1rnAnswer:
Q. Find the sum of the first 9 terms of the following sequence. Round to the nearest hundredth if necessary.75,66,58.08,…Sum of a finite geometric series:Sn=1−ra1−a1rnAnswer:
Identify terms and ratio: Identify the first term a1 and the common ratio r of the geometric sequence.The first term a1 is the first number in the sequence, which is 75.To find the common ratio r, we divide the second term by the first term.r=7566=0.88
Use sum formula: Use the formula for the sum of the first n terms of a geometric series.We have a1=75, r=0.88, and n=9. The formula for the sum of the first n terms (Sn) of a geometric series is:Sn=1−ra1−a1⋅rn
Substitute and calculate: Substitute the values into the formula and calculate the sum.S9=1−0.8875−75×0.889Now we calculate the numerator and the denominator separately.Numerator: 75−75×0.889Denominator: 1−0.88
Calculate numerator: Calculate the numerator.75−75×0.889=75−75×(0.23357214690901212)≈75−17.5179≈57.4821
Calculate denominator: Calculate the denominator.1−0.88=0.12
Divide to find sum: Divide the numerator by the denominator to find the sum.S9=0.1257.4821≈479.0175
Round the result: Round the result to the nearest hundredth if necessary. S9≈479.02
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