Q. Find the sum of the first 9 terms of the following series, to the nearest integer.2,25,825,…Answer:
Identify pattern: Identify the pattern of the series.The given series is 2,25,825,… which looks like a geometric series. To confirm this, we need to find the common ratio by dividing the second term by the first term and the third term by the second term.Common ratio (r)=225=45And, r=25825=825×52=45Since the common ratio is the same for these terms, we can confirm that this is a geometric series with a common ratio of 45.
Use formula for sum: Use the formula for the sum of the first n terms of a geometric series.The sum of the first n terms of a geometric series is given by the formula: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=2, r=5/4, and n=9.
Substitute and calculate: Substitute the values into the formula and calculate the sum.S9=2×(1−(45)9)/(1−45)Since 45 is greater than 1, the series is divergent, and we need to adjust the formula to account for this:S9=2×((45)9−1)/(45−1)S9=2×((45)9−1)/(41)Now, calculate (45)9:(45)9=4959
Calculate 59 and 49: Calculate 59 and 49.59=195312549=262144Now we can continue with the calculation of S9:S9=2×(2621441953125−1)/(41)
Simplify expression: Simplify the expression.S9=2×(2621441953125−262144262144)/(41)S9=2×(1953125−262144)/262144/(41)S9=2×(2621441690981)×4S9=2×655361690981S9=655363381962
Divide for sum: Divide to find the sum to the nearest integer.S9≈655363381962S9≈51.6To the nearest integer, the sum is approximately 52.
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