To solve the problem, we need to multiply the distance each runner will run by the number of runners and get the total distance of the race. So we have:
distance per runner = 3/8 mile
number of runners = 4
total distance = distance per runner x number of runners
total distance = 3/8 x 4
total distance = 12/8 miles
To simplify the answer, we can divide both the numerator and denominator by 4, which gives us:
total distance = 3/2 miles
Therefore, the race is 3/2 miles long.