Can some please help me on this problem?? I think I’m setting it up wrong...

Accepted Solution

Answer:   60 miles per hourStep-by-step explanation:Let s represent the speed in miles per hour during the first part of the trip. Then s-10 will be the speed during the last part of the trip.For speed/time/distance problems, the appropriate relation is the one that is posted on every speed limit sign:   speed = miles/hour = distance/timeRearranging this relation gives you the expression for time:   time = distance / speedYou are given time and distance and you need to find speed. The time you're given is the total for the two parts of the trip, so ...   4 = 84/s + 130/(s-10) . . . . . . total time = time1 + time2Multiplying by the product of the denominators, this becomes ...   4s(s-10) = 84(s-10) +130s   4s^2 -254s +840 = 0 . . . . . . subtract the right side to put in standard formThis can be solved using any of several methods for solving quadratic equations. Solutions are ...   s = 60, s = 3.5 . . . . . only the first solution makes any sense in the problemThe speed during the first part of the trip is 60 miles per hour.