Question

Observe the graph given below for charges required in a library.
So, one should pay for spending 10 hours in the library.

• A. $10
• B. $7
• C. $8
• D. $15

Answer 1

The correct option is D $15

Consider the points $(2,8.6)$ and $(4,10.2)$
Intial value = y-intercept = $\$7$.

You know,
Slope = rate of change = $\frac{Changeiny}{Changeinx}$
$=\frac{y_2-y_1}{x_2-x_1}$

Putting the values you get,
Slope = $\frac{10.2-8.6}{4-2}$
= $\frac{1.6}{0.2}$
= $0.8$/hour
You know, equation of a straight line is $y=mx+c$ where c represents the y-intercept value.

∴ By putting values, you get,
Equation of the line is $y=0.8x+7$

So, when the time spent will be 10 hours,
the payment to be made is $=0.8\times 10+7=\$8+\$7=\$15$.