Writing and evaluating a function

Introduction

In this lesson, given a real-world situation, we write a function to model the problem and then evaluate it for a particular situation or value.

Example 1

Moe has savings of 70andheearns5 for each hour of lawn mowing. If A is the amount with Moe and h is the number of hours he works, write an equation in A and h. Find how much amount he has after 6 hours of mowing lawn.

Solution

Step 1:

Equation in A and h, A = 70 + 5h; h = 6

Step 2:

A = 70 + 5h = 70 + 56 = 70 + 30 = $100;

So, total amount with Moe = A = $100

Example 2

Stacy is putting 270inasavingsaccountandadding40 each week. Let S represent the total amount saved and let w represent the number of weeks Stacy has been adding money. Write an equation relating S and w and use it to find the total amount after 12 weeks.

Solution

Step 1:

Equation in S and w, S = 270 + 40w; w = 12

Step 2:

S = 270 + 40w = 270 + 4012 = 270 + 480 = $750;

So, Total amount = S = $750