Q. Find the sum of the first 38 terms of the following series, to the nearest integer.3,9,15,…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=9−3=6
Use arithmetic series formula: Use the formula for the sum of an arithmetic series.The sum of the first n terms of an arithmetic series can be found using the formula:Sn=2n×(2a+(n−1)d)where Sn is the sum of the first n terms, a is the first term, and d is the common difference.
Plug in values: Plug in the values into the formula to find the sum of the first 38 terms.Let's use the formula with n=38, a=3, and d=6.S38=238×(2×3+(38−1)×6)
Simplify expression: Simplify the expression to find the sum.S38=19×(6+37×6)S38=19×(6+222)S38=19×228S38=4332