The increase of the radius is a linear increase since we have the constant rate of 0.07 inches per second
The equation for a linear growth/decay is given by the form

where

is the rate of increase and

is the value of

when

We have

when
So the equation is 
The length of the radius when

seconds is


inches
Answer:
Eudora spent 0.5 hours from home to library and 1.5 hours from library to school
Step-by-step explanation:
Given
Home to Library:
-- Average Speed
Library to School
-- Average Speed
Total


Required
Determine the time taken from home to library and from library to school
Let the time spent from home to library be x. So, from library to school will be: 2 - x
So, we have:
Home to Library:
-- Average Speed
-- Time
Library to School
-- Average Speed
-- Time
Distance is calculated as:

Home to Library:



Library to School:



The total distance is 120km. So, we have:


Collect Like Terms



Solve for x


Recall that:


So, we have:

