Q. Find the sum of the first 38 terms of the following series, to the nearest integer.9,12,15,…Answer:
Identify type and difference: Identify the type of series and the common difference.The given series is arithmetic because there is a constant difference between consecutive terms.To find the common difference d, subtract the first term from the second term.d=12−9=3
Find first term and number: Find the first term a and the number of terms n. The first term a is given as 9. The number of terms n to sum up is given as 38.
Use sum formula: Use the formula for the sum of the first n terms of an arithmetic series.The formula is Sn=2n×(2a+(n−1)d).Now plug in the values of a, n, and d into the formula.S38=238×(2×9+(38−1)×3)
Simplify expression: Simplify the expression.S38=19×(18+37×3)S38=19×(18+111)S38=19×129
Calculate sum: Calculate the sum.S38=19×129S38=2451