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Interpreting Rate of Change & Initial Value · Easy Worksheet 1

Interpreting Rate of Change & Initial Value — Easy Worksheet 1

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 C = 25h + 74 gives the cost C, in dollars, of renting a boat for h hours. What does the number 74 represent: the rate of change or the initial value?
2 The equation S = 8n + 118 gives the money S, in dollars, in Lena's savings account after n weeks. What does the number 8 represent: the rate of change or the initial value?
3 The equation H = 3w + 11 gives the height H, in centimeters, of a plant w weeks after it was planted. What does the number 11 represent: the rate of change or the initial value?
4 The equation S = 22n + 179 gives the money S, in dollars, in Lena's savings account after n weeks. What does the number 179 represent: the rate of change or the initial value?
5 The equation F = 2d + 9 gives the fare F, in dollars, for a taxi ride of d miles. What does the number 2 represent: the rate of change or the initial value?
6 The equation P = 8g + 32 gives the monthly phone bill P, in dollars, when g gigabytes of data are used. What does the number 32 represent: the rate of change or the initial value?
7 The equation H = 6w + 5 gives the height H, in centimeters, of a plant w weeks after it was planted. What does the number 5 represent: the rate of change or the initial value?
8 The equation C = 29h + 20 gives the cost C, in dollars, of renting a boat for h hours. What does the number 29 represent: the rate of change or the initial value?

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