Question

Evaluate the series. A)125 B) 38 C) 210 D) 165

Answer 1

165 is answer we also use a formula
5 ( n/2(2a + ( n-1)d)
in that n=6 ,a=3 , d= 1

Answer 2

Answer:

Option D). 165

Step-by-step explanation:

The given expression is $\sum_{n=3}^{8}5n$

By using the expression we get an arithmetic series

15, 20, 25........6 terms

Now we will calculate the sum of 6 terms of this sequence

$\sum_{n=3}^{8}5n=6/2[2\times 15+(6-1)\times 5]$

$=3(30+25)=3\times 55=165$

Therefore sum of this sequence is 165.