Question

Carlos bought a new cell phone. The graph represents the

relationship between the number of minutes he uses
and the total
cost. What is the equation of the line?

A) y= 5x + 0.1
B) y=0.1x + 5
C) y=0.5x + 5
D) y = 5x + 5

Answer 1

B : y = 0.1x + 5

Explanation:

using the y = mx + b equation

b is the intercept on the y axis ( x = 0)

m is the slope of the line.

From the graph we can see that the intercept is (0,5), therefore b = 5;

To calculate slope (m) pick two pints on the line e.g (100, 15) and (0, 5)

m = (y2 - y1)/(x2 -x1) = (15 - 5)/(100 - 0) = 10/100 = 0.1

m = 0.1

therefore in y = mx + b

y = 0.1x + 5