<PRE><B>Question 518399</B>
A TRUCK DRIVER TRAVELED AT 40mph for the first part of a 646-miletrip, then increased his speed to 58 mph for the rest of the trip. the entire trip took 13 hours. how many hours are traveled at 58 mph?
----
d = distance at 58 mi/hr
d/58 + (646-d)/40 = 13
Multiply by 58*40
40d + 58*(646-d) = 13*40*58 = 30160
40d - 58d + 37468 = 30160
-18d = -7308
d = 406 miles
406 mi/58 mi/hr = 7 hours</PRE>