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6th Edition

Stewart + 5 others

Publisher: Cengage Learning

ISBN: 9780840068071

Chapter 1.11, Problem 48E

**(a)**

To determine

**To express:** The given variation as equation.

Expert Solution

The equation of given variation is

Jointly proportional:

Consider the equation,

Here,

The rate

Mathematically,

Substitute

Here,

Thus, the equation of the given variation is

**(b)**

To determine

**To compare:** The rate of spread of the infection in the two given cases.

Expert Solution

The rate of spread of infection in case 2 as compared to case 1 is 80 times.

**Given:**

Case 1:

Only

Case 2:

**Calculation:**

To calculate, rate of spread of infection

To calculate, rate of spread of infection

Divide equation (2) by equation (3).

Simplify above equation.

Thus, the rate of spread of infection when

**(c)**

To determine

**To find:** The rate of spread of infection when entire population is infected.

Expert Solution

The rate of spread of infection is zero.

**Calculation:**

If all the population is infected the value of

Thus, rate of spread of infection is zero.

This answer makes intuitive sense because if all the peoples are infected there is no one left to be infected. Hence rate of spread of infection is zero.