Problem Solving

A bicyclist travels uphill from town A to town B for 2 hours at an average speed of 4 miles per hour and returns along the same road at an average speed of 6 miles per hour. What is the bicyclist’s average speed for the round trip, in miles per hour?
1) 4 4/5
2)5
3)5 1/5
4)5 2/5
5)5 3/5

I keep getting five as the answer from solving for D, getting the total distance as 16, solving for the total travel time as 3.20 hours, then plugging those in the RT=D equation to solve for R. But the answer is 4 4/5.
What am I doing wrong?
Thanks

maolivie wrote:A bicyclist travels uphill from town A to town B for 2 hours at an average speed of 4 miles per hour and returns along the same road at an average speed of 6 miles per hour. What is the bicyclist’s average speed for the round trip, in miles per hour?
1) 4 4/5
2)5
3)5 1/5
4)5 2/5
5)5 3/5

I keep getting five as the answer from solving for D, getting the total distance as 16, solving for the total travel time as 3.20 hours, then plugging those in the RT=D equation to solve for R. But the answer is 4 4/5.
What am I doing wrong?
Thanks

I think total time is 3 hrs and 20 min, not 3.2 hours

16 / (2 + 8/6)
= 16 * 6 / (12 + 8 )
= 16 * 6 / 20
= 24 / 5
= 4 4/5

AHHH, yeah you are right!

I make a lot of stupid mistakes like that