Question

Find the sum of the arithmetic series given ai = 45, an = 85, and n = 5.

Answer 1

Answer:

C. 325.

Step-by-step explanation:

The last term a5 = 85

a1 = 45

Sum of n terms = n/2 (a1 + l)

So here we have n = 5, a1 = 45 and the last term l = 85

= (5/2)(45 + 85)

= 5/2 * 130

= 325.

Answer 2

The required sum of the arithmetic series is 325.

Arithmetic series is defined as a sequence of numbers arranged in a particular pattern.

The sum of the nth term of an arithmetic sequence is expressed as:

$S_n = \frac{n}{2}[a+l]$ where:

n is the number of terms

a is the first term

l is the last term

Given the following

a = 45

n = 5

an = l = 85

Substitute the given values in the formula above:

$S_5= \frac{5}{2}(45+85)\\ S_5=\frac{5}{2}(130)\\ S_5=5 \times 65\\S_5=325$

Hence the sum of the arithmetic series is 325

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