Q. Find the sum of the first 7 terms of the following series, to the nearest integer.25,100,400,…Answer:
Identify type and ratio: Identify the type of series and the common ratio.The given series is geometric because each term after the first is obtained by multiplying the previous term by a constant number.To find the common ratio r, we divide the second term by the first term.25100=4Common Ratio: 4
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, r is the common ratio, and n is the number of terms.In this case, a=25, r=4, and n=7.
Substitute and calculate: Substitute the values into the formula and calculate the sum.S7=25×(1−47)/(1−4)S7=25×(1−16384)/(1−4)S7=25×(−16383)/(−3)S7=25×5461S7=136525
Round to nearest integer: Round the sum to the nearest integer.The sum of the first 7 terms is 136525, which is already an integer, so no rounding is necessary.