Question

Find the sum of the sequence.a1 = 1, d = 2,n = 10

Answer 1

This problem is about arithmetic sequence.

We know that

$a_1=1,d=2,n=10$

This means the first element is 1, the difference to form the sequence is 2, and the total number of elements is 10.

Now, we use the following formula to sum all 10 elements.

$S_n=\frac{n}{2}(2a_1+(n-1)d)$

Using all the given information, we have

$S_{10}=\frac{10}{2}(2(1)+(10-1)2)$

We need to solve all those parentheses.

$S_{10}=5(2+9\cdot2)\rightarrow S_{10}=5(2+18)=5(20)=100$

Therefore, the sum of the given arithmetic sequence is 100.