Let the slower runners speed be X kilometers per hour.
Then the faster runners speed would be X+2 kilometers per hour.
The formula for distance is Speed times time.
The distance is given as 30 kilometers and time is given as 3 hours.
Since there are two runners you need to add the both of them together.
The equation becomes 30 = 3x + 3(x+2)
Now solve for x:
30 = 3x + 3(x+2)
Simplify:
30 = 3x + 3x +6
30 = 6x + 6
Subtract 6 from each side:
24 = 6x
Divide both sides by 6:
x = 24/6
x = 4
The slower runner ran at 4 kilometers per hour.
The faster runner ran at 4+2 = 6 kilometers per hour.
This is a typical radioactive decay problem which uses the general form:
A = A0e^(-kt)
So, in the given equation, A0 = 192 and k = 0.015. We are to find the amount of substance left after t = 55 years. That would be represented by A. The solution is as follows:
A = 192e^(-0.015*55)
<em>A = 84 mg</em>
