Question 768713
the average rate of a bus is 15 miles per hour more than that of an average truck. the truck takes 1 hour more than the bus to drive 90 miles, how long does it take the bus
---------
Bus DATA:
distance = 90 miles ; rate = r+15 mph ; time = 90/(r+15) hrs.
-------
Truck DATA:
distance = 90 miles ; rate = r mph ; time = 90/r hrs.
--------
Equation:
truck tme - bus time = 1 hour
90/r - 90/(r+15) = 1
----
90(r+15) - 90r = r^2+15r
------
r^2 + 15r - 1350 = 0
---
(r-30)(r+45) = 0
------
Positive solution:
r = 30 mph (truck speed)
r+15 = 45 mph (bus speed)
================================
Cheers,
Stan H.
================================


----