Dave drove 55 mph for part of the trip and 60mph for the rest. The 245 mile trip took him 4 hours 12 minutes. How long did the 2nd part of the trip take? How far did he drive during the 2nd part of his trip?

Dave drove 168 miles during the 2nd part of the trip

Step-by-step explanation:

1. Let's review the information given to us to answer the question correctly:

Speed of Dave for part of the trip = 55 mph

Speed of Dave the rest of the trip = 60 mph

Total time of the round trip = 4 hours 12 minutes

Total distance of the trip = 245 miles

2. How far did Dave drive during the 2nd part of his trip?

Let's recall that the formula of speed is:

Speed = Distance/Time, therefore Distance = Speed * Time

x = Time of part of the trip

4 hours 12 minutes - x = Time of the rest of the trip

4.2 hours - x = Time of the rest of the trip

Now, we can write solve for x, this way:

55 * x + 60 (4.2 - x) = 245

55x + 252 - 60x = 245

-5x = 245 - 252

-5x = - 7

x = - 7/-5 = 7/5 = 1.4 ⇒ 4.2 - x = 2.8

1st part of the trip = 55 * 1.4 = 77 miles

2nd part of the trip = 2.8 * 60 = 168 miles

Dave drove 168 miles during the 2nd part of the trip and 77 miles during the 1st part