Answer:
The unit rate in miles per hour = <em>1.4 miles/hr</em>
Step-by-step explanation:
Given that:
Distance walked by Boardman family = Two over five of a mile = 
Time taken by Boardman family = Two over seven of an hour = 
To find:
The unit rate in the miles per hour = ?
Solution:
Formula for the rate or the speed can be given as:

Putting the values:

So, the unit rate in miles per hour = <em>1.4 miles/hr</em>
The population starts at 2000, so a=2000.
We also know that the population in 3 hours is 1000, so we can setup the equation:
2000 b^3 = 1000
This gets us:
b^3 = 1/2
And taking the cube root of both sides gives us:
b ≈ 0.7937005259841
Rounding that to 4 places, we have:
f(t) = 2000 (0.7937)^t
My answer is 82. I added up 90 + 80 + 75 = 245. I then divided that by 3 because there are 3 different cultures. And the number was 81. something. So, I rounded and got 82. But I'm not sure if that's the right answer.