Question

A battery is charged. The percentage of the battery's capacity that is charged as a function of time (in minutes) is graphed 50+ 70 50+ Capacity charge 20+ 10 What was the battery's charging level when the charging began? 12

Answer 1

The equation of the line (segment) is:

$y=2x+40$

Where y is the percentage of the charge, and x is the time (in minutes) that has passed since the charge started.

How do we know that? Because we can identify two points in the graph shown in the image:

$(0,40),(5,50)$

Notice that the line intersects the y-axis in point 40 (when the battery had 40% of its charge)

You can easily see that the equation I first wrote is correct by simply substituting the values of those two points I just wrote above.

Since we need 'the battery's charging level when the charging began', we need to set x=0, as we need the value of y (percentage of the charge) when the charging started.

So, if x=, then:

$y=2\cdot0+40=40$

Therefore, the answer is 40%