Answer:
River's length is 7.38 times the race's length, approximately.
Explanation:
- We know that
- The riven is 310 miles long.
- The race is 42 miles long.
So, if we wanna know how many times as long as the race is the river, we just need to use this expression

Where
represents the factor that expresses the ratio between both, solving for
we have

Therefore, river's length is 7.38 times the race's length, approximately.