Question

The sum of an 84-number series is –7,980. What is the sum of the first and last numbers?

A. -380.0
B. -190.0
C. -95.0
D. -47.5

Answer 1

We know, S = n/2 [a + l]

Substitute the known values,
-7980 = 84/2 [a + l ]
a + l = -7980/42

a+l = -190

In short, Your Answer would be: Option B

Hope this helps!

Answer 2

Option B. -190

Explanation:

Since the sum of 84 number series is -7980.

We have to find the sum of first and last numbers.

Since sum of an arithmetic sequence is represented as

`S=(n)/(2)(first+last)`

S =
`-7980=(84)/(2)(First+last)=42(first+last)`

(First + last) =
`(-7980)/(42)=(-190)`

So the total of first and last term is (-190).

Option B. -190 is the correct option.