The graph shows the correlation between ambient air temperature, t, in degress Fahrenheit and the number of chirps, c, per minute that a snowy tree cricket makes at that temperature. Which of the following equations represents the line shown in the graph ?

Options

A. `c = 4t -160`
B. `c = 1/4 t -160`
C. `c = 1/2 t -40`
D. `c =4t+160`

Answer

A

Explanation

Start by finding the slope of the line by picking a pair of points, such as `(40,0) and (65,100):m = (1---0)/(65-40) =(100)/(15)=4.` Choices (B) and (C ) have slopes other than 4, so eliminate them. Choice (A) and (D) have y-intercepts of -160 and 40, respectively. Now real the axis labeels carefully : the horixzontal axis begins at 40 (not 0). The line is trending downward as x-values get smaller, so the y-intercept (when x=0) must be well below 0 on the verttical axis. Therefore, the answer must be (A).