The arithmetic progression is given by the formula аn = 3n + 2. Find the sum of the first twenty members.

univerkov | July 18, 2021 | education

Let’s find the first and twentieth term of the progression.

a1 = 3 * 1 + 2 = 5;

a20 = 3 * 20 + 2 = 62.

Let’s find the sum of its first twenty members.

S20 = (a1 + a20) / 2 * 20 = (5 + 62) / 2 * 20 = 670.

Answer: S20 = 670.

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