Why below question needs AVERAGE current?

Question

The current in a component is reduced uniformly from 100 mA to 20 mA over a period of 8.0 s.

What is the charge that flows during this time?

A 160 mC B 320 mC C 480 mC D 640 mC

Answer is C

my doubt is why find the average current as that is the method i saw on google ?

Answer 1

Current can be thought of as charge/time, meaning that it is a measure of the amount of charge that passes a point during an interval of time.

Notice that the question states that the current is reduced uniformly from 100 mA to 20 mA. Because the reduction of current is uniform, the total amount of charge that flows from the fluctuating current would be equal to the total amount of charge that flows from a constant current of 60 mA (average of 100 and 20) over the time period of 8 seconds.

By using the average, we will be easily able to isolate charge from the equation current = charge/time.

Solving for q (charge) we get:

60 = q/8

60(8) = q

480 mC = q