Sid has a job at morgan motors. the salary is $1200 a month, plus 3% of the sales price of every car or truck sid sells (this is called a commission). (a) the total of the sales prices of all the vehicles sid sold during the first month on the job was $72000. what was sid's income (salary plus commission)? (b) in order to make $6000 in a single month, how much selling must sid do? (c) write a linear equation that expresses sid's monthly income y in terms of the value x of the vehicles sid sold. (d) graph this equation. what is the meaning of its y-intercept, and the meaning of its slope?

Montly salary = 1200 + 3% * price = 1,200 + 0.03p

a) price = 72,000 => 1200 + 3%* 72,000 = 1200 + 0.03*72,000 = 3,360

Answer 1:  3,360 

b) salary = 6,000 => 6,000 = 1,200 + 0.03p => p = [6000 - 1200] / 0.03 = 160,000

Answer 2: 160,000

c) linear equation

salary = y; price = x

y = 1200 + 0.03x

Answer 3: y = 1200 + 0.03x

d) graph

- slope: is the coefficient of the independent variable, x: 0.03

It means the increase of salary per unit of price of the vehicles sold

- y intercept: it is the constant value of the linear equation: 1200

It represents the salary if Sid does not sell any vehicle.

- The graph is a straight line: y = 1200 + 0.03x

- You can use two points to draw the line.

- Use x = 0, for which y = 1200 and

 x = 100,00 for which y = 1200 + 0.03*100,000 = 1200 + 30,0000 = 31200

- Use an adequate scale. I suggest that every division of the x-axis be $10,000 or $20,000; and every division of the y-axis be $1000

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