Question

If tñ=2ñ+3, find S10​

Answer 1

Answer:

$S_{10}=280$

Step-by-step explanation:

Given that,

$t_n=2n+3$ ...(1)

We need to find the value of $S_{10}$.

Put n = 1 to find the first term.

$t_1=2(1)+3=5$

Put n = 2 to find the second term.

$t_2=2(2)+3=7$

Put n = 3 to find the third term.

$t_3=2(3)+3=9$

Put n = 10 to find the tenth term.

$t_{10}=2(10)+3=23$

It means we need to find the sum of 5,7,9,.....,23.

The formula for the sum of n terms is given by :

$S_=\dfrac{n}{2}(a+a_n)$

We have, n = 10, a = 5 and $a_n=23$

So,

$S=\dfrac{10}{2}(5+23)\\\\S_{10}=10\times 28\\\\=280$

So, the value of $S_{10}$ is equal to 280.