You must travel at 42 mph for 4 hours
<em><u>Solution:</u></em>
Time varies inversely as rate of motion
Let "t" be the time required
Let "r" be the rate of motion
Then, we get
Where, "k" is the constant of proportionality
<em><u>You travel 3 hours at a rate of 56 mph</u></em>
Substitute t = 3 and r = 56 in eqn 1
<em><u>Find the rate you must travel for 4 hours</u></em>
r = ? and t = 4
Substitute t = 4 and k = 168 in eqn 1
Thus you must travel at 42 mph for 4 hours