FINDING AVERAGE OR INSTANTANEOUS RATE OF CHANGE FROM A TABLE

Definition of average rate of change :

The average rate of change between x = a and x = b is the slope of the secant line of the curve between the points x = a and x = b

Average rate of change =f(b)-f(a)b-a(or)Average rate of change =yx (or)Average rate of change =y2-y1x2-x1

Instantaneous rate of change :

The instantaneous rate of change at a point x = a is the slope of the tangent line of the curve at the point x = a.

Instantenous rate of change f '(a)=lim h0f(a+h)-f(a)h
difference-between-rate-of-change

Problem 1 :

Use the following table to find the average rate of change on the given interval.

rate-of-change-q1

1. [3, 13]

2. 0 ≤ x ≤ 12

3. [3, 4]

Solution:

1. [3, 13]

Average Rate of Change=Change in Outputchange in Input=10-413-3=610=35 feet/min

2. 0 ≤ x ≤ 12

Average Rate of Change=Change in Outputchange in Input=5-(-2)12-0=712 feet/min

3. [3, 4]

Average Rate of Change=Change in Outputchange in Input=-7-44-3=-111=-11 feet/min

Problem 2 :

The function h(x) is given in the table below. Which of the following choices shows the average rate of change of the function over the interval 2 ≤ x ≤ 6?

rate-of-change-q2
(1)-32
(2) 64
(3) -76
(4) -1

Solution:

Average Rate of Change=Change in Outputchange in Input=3-96-2=-64=- 32

So, option (1) is correct.

Problem 3 :

Given the functions g(x), f(x) and h(x) shown below.

rate-of-change-q3

The correct list of functions ordered from greatest to least by average rate of change over the interval 0 ≤ x ≤ 3 is

A. f(x), g(x), h(x)        B. h(x), g(x), f(x)  

C. g(x), f(x), h(x)        D. h(x), f(x), g(x)

Solution:

g(x) = x2 - 2x

For the average rate of change of a function between x = 0 and x = 3.

Average Rate of Change=7-13-0=63=2

For the function 'g',

g(x) = x2 - 2x

g(3) = 32 - 2(3)

= 9 - 6

= 3

g(0) = 02 - 2(0)

= 0

Therefore average rate of change=3-03-0=33=1

h(3) = 9

h(0) = 2

Average Rate of Change=9-23-0=73=2.3

Therefore, order of rate of change from greatest to the least for the given functions will be,

h(x) > f(x) > g(x)

So, option (D) is correct.

Problem 4 :

Use the table below to estimate the value of d'(120). Indicate units of measures.

rate-of-change-q4

Solution:

d'(120) = 180 - 60

=808-412180-60=396120=3.3 feet/sec

Problem 5 :

Frank is selling lemonade. The function g(t) = (t2 + 4)/2 models the number of glasses he sold, g(t), after t hours. What is the average rate of change between hour 2 and hour 6? Show all work.

Solution:

g(t)=t2+42g(2)=22+42=4+42g(2)=4g(6)=62+42=36+42g(6)=20 Average Rate of Change=20-46-2=164=4 glasses/hour

Problem 6 :

The table shows the average diameter of a person's pupil as a person ages. What is the average rate of change of a person's average pupil diameter from age 30 to 70? Be sure to include units.

rate-of-change-q6

Solution:                                                                              

Average rate of change=2.7-4.370-30=-1.6 40=-0.04

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