Q. Find the sum of the first 8 terms of the following series, to the nearest integer.3,415,1675,…Answer:
Identify Pattern: Identify the pattern of the series.The series is geometric because each term is multiplied by a common ratio to get the next term. To find the common ratio (r), divide the second term by the first term.r=315/4=415⋅31=1215=45
Use Formula: Use the formula for the sum of the first n terms of a geometric series, which is Sn=1−ra1(1−rn), where a1 is the first term, r is the common ratio, and n is the number of terms.Here, a1=3, r=45, and n=8.
Calculate Sum: Calculate the sum of the first 8 terms using the formula.S8=1−453(1−(45)8)
Simplify Denominator: Simplify the denominator of the fraction.1−45=44−45=−41
Calculate Exponent: Calculate (45)8 to find the numerator.(45)8 is a large number, so it's best to use a calculator for this step.
Substitute and Calculate: Substitute the values into the sum formula and calculate.S8=−413(1−(45)8)Using a calculator, (45)8≈1525.87890625S8=−413(1−1525.87890625)
Simplify Numerator: Simplify the numerator.1−1525.87890625≈−1524.87890625S8=−413(−1524.87890625)
Multiply and Divide: Multiply the numerator by 3 and divide by the denominator.S8=−41−4574.63671875S8=−4574.63671875⋅(−4)S8=1830.6546875
Round to Nearest: Round the sum to the nearest integer.S8≈1831
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