Q. Find the sum of the first 10 terms of the following series, to the nearest integer.21,126,756,…Answer:
Identify Series Type: Identify whether the given series is geometric or arithmetic. In the given series, each term is a multiple of the previous term, which suggests that the series is geometric.
Find Common Ratio: Identify the common ratio of the geometric series.To find the common ratio, divide the second term by the first term.Common Ratio r = 21126 = 6
Use Sum Formula: Use the formula for the sum of the first n terms of a geometric series.The formula for the sum of the first n terms (Sn) of a geometric series is:Sn=a⋅(1−rn)/(1−r), where a is the first term and r is the common ratio.
Calculate Sum: Calculate the sum of the first 10 terms using the formula.First term (a)=21Common Ratio (r)=6Number of terms (n)=10S10=21×(1−610)/(1−6)
Perform Calculations: Perform the calculations.S10=21×(1−60466176)/(1−6)S10=21×(−60466175)/(−5)S10=21×12093235S10=253958535
Round Sum: Round the sum to the nearest integer.The sum is already an integer, so no rounding is necessary.