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Average Rate of Change Formula

The Average Rate of Change Formula calculates the slope of a line or a curve on a given range. It is defined as the ratio of the difference in the function f(x) as it changes from 'a' to 'b' to the difference between 'a' and 'b'. The average rate of change is denoted as A(x).

Average Rate of Change Formula for a function f(x) in the range (a,b) is,
Average Rate of Change Formula

Where,
f(a) and f(x) are the value of the function f(x) at the range 'a' and 'b'.
a and b are the range limit.

Related Calculators
Average Rate of Change Calculator Calculating Rate of Change
Instantaneous Rate of Change Calculator Average Calculator
 

Average Rate of Change Problems

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Some solved problems based on average rate of change are given below:

Solved Examples

Question 1: Calculate the average rate of change of a function, f(x) = 2x + 11 as x changes from 2 to 7 ?
Solution:
 
Given,
f(x) = 2x + 11
a = 2
b = 7

f(2) = 2(2) + 11
f(2) = 4 + 11
f(2) = 15

f(7) = 2(7) + 11
f(7) = 14 + 11
f(7) = 25

The average rate of change is,
A(x) = $\frac{f(b)-f(a)}{b-a}$

A(x) = $\frac{f(7)-f(2)}{7-2}$

A(x) = $\frac{25-15}{5}$

A(x) = $\frac{10}{5}$

A(x) = 2

 

Question 2: A function is given as, f(x) = x2 + 2. Calculate the average rate of change of the function if the range of x is (5, 15) ?
Solution:
 
Given,
f(x) = x2 + 2
a = 5
b = 15

f(5) = (5)2 + 2
f(5) = 25 + 2
f(5) = 27

f(15) = (15)2 + 2
f(15) = 225 + 2
f(15) = 227

The average rate of change is,
A(x) = $\frac{f(b)-f(a)}{b-a}$

A(x) = $\frac{f(15)-f(5)}{15-5}$

A(x) = $\frac{227-27}{10}$

A(x) = $\frac{200}{10}$

A(x) = 20

 

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