Question 898767
You and your friend part at an intersection.
 You drive off north at a constant speed, and your friend drives east at a speed that is 9 mph higher.
 After 3 hours the distance between you and your friend is 282.78 miles.
:
let s = your driving speed
then
(s+9) = your friend's
:
In 3 hrs: 
3s = your driving dist
(3(s+9) = your friend's dist
:
this is a rt triangle problem, a^2 + b^2 = c^2, where
a = 3s
b = 3(s+9)
c = 282.78
:
(3s)^2 + (3(s+9))^2 = 282.78^2
9s^2 + (3s+27)^2 = 79964.53
9s^2 + 9s^2 + 81s + 81s + 729 - 79964.53 = 0
18s^2 + 162s - 79235.53 = 0
Using the quadratic formula, I got:
s = 62 mph is your speed
:
:
Check this on your calc:
3*62 = 186 mi
3*71 = 213 mi
enter: {{{sqrt(186^2+213^2)}}}








 You have been driving at _______ mph.