Question

A catering company uses a linear function to determine the total cost of parties. The following table shows the costs for dinner parties with varied numbers of guests. What is the cost to cater a dinner party with 90 guests?

Guests
Total Cost
30
$315
60
$555
$720
$795
$870
$945

Answer 1

From the two given points (30, 315) and (60, 555) the rate per guest is (555−315)/(60−30) = 240/30 = $8 per guest.
Find the fixed cost: 315 = 8(30) + b → b = 75. So total cost C(g) = 8g + 75.

For 90 guests: C(90) = 8(90) + 75 = 720 + 75 = $795.