7 hours 8 9.4

Question

Greg drove at a constant speed in a rainstorm for
250
miles. He took a? break, and the rain stopped He then drove
112
miles at a speed that was
6
miles per hour faster than his previous speed. If he drove for
7
?hours, find the? car's speed for each part of the trip.

Answer 1

solve: 250/S+112/(S+6)=7 where S is the speed at the first segment of the trip; upon solving this equation: S=50 miles/hr and the next sement speed which is 6 miles more =56

Good luck

Answer 2

Hi Jessica,

Since the distance is equal to the rate times the time, the first part of the trip can be described as  250 = rt and the second part of the trip is 

112 = (r+6)(7-t).  Solve the first equation for either of the variables lets say t. Then t = 250/r. Substituting this value of t into the second equation produces  112 = (r+6)(7-250/r). Use the distributive property on the right side gives us  112 = 7r - 250 + 42 - 1500/r. Combine like terms and multiply both sides by r to get

                112r = 7r² - 208r - 1500 Rewrite the equation in standard form as         0 = 7r² - 320r - 1500  Use the quadratic formula to get the value of r to be 50 or -30/7. Since it makes no sense to have a negative time, ignore the negative solution and use r = 50 for the first part of the trip and 56 for the second part of the trip.