Question

Naomi wants to buy a new computer for $840. She is considering two payment plans that require weekly payments.

Part A:
Write a linear equation that models each payment plan. Write your answers in slope intercept form. Explain why you decided which one is your slope and which one is your y-intercept.
Plan A: $180 down $60/wk payments
Plan B: $0 down $70/wk payments

Answer 1

Linear equations take the form: y = mx + c

y is the dependent variable i.e the money that Naomi has to pay in total.

x is the independent variable which in this case is weeks.

m is the slope and this shows the change as a result of x. It should therefore represent the weekly payment as this is increases per week.

c is a the y-intercept which means its a fixed figure that doesn't change. It will therefore be the down payment because that does not change.

Plan A:

Naomi wants to pay $840. Using the formula format and explanation above (replace x with w so it makes more sense), the formula will be:

840 = 60w + 180

Plan B:

This has no down payment so there will be no y-intercept.

840 = 70w