Question

test grade vs. time spent studying
mr. martin gave a test to his students. he graphed how many hours the students spent studying and how they scored on the test. what is the equation of the line of best fit above?
a. $y = \frac{20}{3}x + 30$
b. $y = \frac{2}{3}x + 30$
c. $y = \frac{40}{3}x + 30$
d. $y = \frac{4}{3}x + 30$

Explanation:

Step1: Find y-intercept

The line crosses y-axis at (0,30), so b=30.

Step2: Calculate slope

Pick two points on the line: (0,30) and (6,110). Slope $m=\frac{110-30}{6-0}=\frac{80}{6}=\frac{40}{3}$.

Step3: Form equation

Line equation: $y=mx+b=\frac{40}{3}x+30$.

Answer:

C. $y = \frac{40}{3}x + 30$