A farmer drove an average of 30mph for a 9hr trip. During the first 4hrs, he drove 40 mph. Find the speed at the last 5hrs.

Question

i need help solving this! like how to do it as well 

Answer 1

The total miles of the trip is 30 mph times 9 hours which is 270 miles.

 

He drove 40 mph for 4 hours for 160 miles.

 

For the remainder of the trip, he drove 270 - 160 or 110 miles.

 

We also know that he drove for 5 more hours, so he drove 110 miles/ 5 hours which is 22 miles per hour.

Answer 2

We know that the total distance of the trip was 270 miles from (rate*time = distance). This should equal the distance traveled at 40mph for 4 hours plus the rate they traveled for 5 hours. The equation looks like: 

 

4hrs.(40mph) + rate(5hrs) = 30mph(9hrs.) 

 

160mi. + rate(5hrs.) = 270mi.

 

rate(5hrs) = 110mi. 

 

Rate = 110mi./5hrs.

 

rate = 22mph