Use the indicated formula to find the sum.
-$$\text { Use } S = \frac { n ( n + 1 ) } { 2 } \text { to find the sum of } 1 + 2 + 3 + \ldots + 400 \text {. }$$
A)8020
B)80,200
C)79,800
D)80,000

Question

Quizplus · Accepted Answer

The formula $S = \frac{n(n + 1)}{2}$ is used to find the sum of the first $n$ natural numbers. Here, $n = 400$, so substituting $400$ into the formula gives $S = \frac{400(400 + 1)}{2} = \frac{400 \times 401}{2} = 80,200$.

Use the Indicated Formula to Find the Sum Use S=n(n+1)2 to find the sum of 1+2+3+…+400. \text { Use } S = \frac { n ( n + 1 ) } { 2 } \text { to find the sum of } 1 + 2 + 3 + \ldots + 400 \text {. } Use S=2n(n+1)​ to find the sum of 1+2+3+…+400.

Use the Indicated Formula to Find the Sum $\text { Use } S = \frac { n ( n + 1 ) } { 2 } \text { to find the sum of } 1 + 2 + 3 + \ldots + 400 \text {. }$