we are given
first term is

common ratio is

now, we can find nth term

now, we can plug values

now, we can write in sigma form

now, we can find sum
we can use formula

now, we can plug values
we get


so, option-D.................Answer
Answer:

Step-by-step explanation:
The composite solid consists of a cylinder and a cone. Therefore, its total volume will be the sum of the volumes of the cylinder and cone:
Volume of the cone: 
Volume of the cylinder: 
Thus, the total volume of the solid is:

Just use the formula 1/2bh
Answer:
b = - 0.432
Step-by-step explanation:
It takes 200 seconds to produce the first widget. And by the 400th widget, it takes only 15 seconds.
Now, the formula that gives the time to make the nth widget is given by
and we have to evaluate the constant b from the above-given conditions.
So, 
⇒ 
Taking log on both sides
b log (400) = log (0.075)
⇒ b = - 0.432 (Answer)
It dosnt necessarily represent the function