Answer:
19%.
Step-by-step explanation:
We have been given that Mark charged a battery. Each minute, the percentage of the battery's capacity that was charged increased by 2.5%. After 17 minutes of charging, the battery was 61.5% full.
We will use slope-intercept form of equation to solve our given problem. We know that the equation of a line in slope-intercept form is: [tex]y=mx+b[/tex], where,
m = Slope of line,
b = The y-intercept or initial value.
Since battery is charged 2.5% per minute, so slope of line would be 2.5.
We are also told that after 17 minutes of charging, the battery was 61.5% full. Now, we will use point [tex](17,61.5)[/tex] to solve for initial value or b as:
[tex]61.5=2.5\cdot 17+b[/tex]
[tex]61.5=42.5+b[/tex]
[tex]61.5-42.5=42.5-42.5+b[/tex]
[tex]19=b[/tex]
Therefore, the battery was 19% full, when the charging began.
