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Interpreting Rate of Change & Initial Value · Easy Worksheet 2

Interpreting Rate of Change & Initial Value — Easy Worksheet 2

Grade 8 · Whoobee    Name: ____________________   Date: __________

Answer each question with "rate of change" or "initial value".

How to solve

In a linear model y = mx + b, the number multiplied by the input variable (m) is the rate of change: how much the output goes up or down for each 1 unit of the input. The number on its own (b) is the initial value: the output when the input is 0, such as a starting amount or a fixed fee. The order of the terms does not matter, so in 40 + 15h the 15 is still the rate of change. A minus sign in front of the rate means the amount goes down.

Example

The equation C = 28h + 32 gives the cost C, in dollars, of renting a boat for h hours. What does the number 28 represent: the rate of change or the initial value?

Answer: rate of change

right so far
1 The equation W = 25t + 108 gives the water W, in liters, in a pool t minutes after a hose is turned on. What does the number 25 represent: the rate of change or the initial value?
2 The equation P = 3g + 15 gives the monthly phone bill P, in dollars, when g gigabytes of data are used. What does the number 3 represent: the rate of change or the initial value?
3 The equation W = 12t + 253 gives the water W, in liters, in a pool t minutes after a hose is turned on. What does the number 253 represent: the rate of change or the initial value?
4 The equation F = 3d + 8 gives the fare F, in dollars, for a taxi ride of d miles. What does the number 8 represent: the rate of change or the initial value?
5 The equation P = 3g + 32 gives the monthly phone bill P, in dollars, when g gigabytes of data are used. What does the number 3 represent: the rate of change or the initial value?
6 The equation S = 22n + 148 gives the money S, in dollars, in Lena's savings account after n weeks. What does the number 148 represent: the rate of change or the initial value?
7 The equation H = 2w + 10 gives the height H, in centimeters, of a plant w weeks after it was planted. What does the number 10 represent: the rate of change or the initial value?
8 The equation W = 15t + 235 gives the water W, in liters, in a pool t minutes after a hose is turned on. What does the number 235 represent: the rate of change or the initial value?

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