Answer:
Option D). 165
Step-by-step explanation:
The given expression is [tex]\sum_{n=3}^{8}5n[/tex]
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
[tex]\sum_{n=3}^{8}5n=6/2[2\times 15+(6-1)\times 5][/tex]
[tex]=3(30+25)=3\times 55=165[/tex]
Therefore sum of this sequence is 165.
