Answer:We will use our famous distance formula:
d = r x t.
Then, rearranging this formula, gives:
t = d/r
Now, t(for 1st 10 mi) = 10/30 = 1/3 hr.
And, t(for 2nd 10 mi) = 10/50 = 1/5 hr.
So, the total time = 1/3 + 1/5 hr.
Rearranging our distance formula again, gives: r = d/t
Now, r(average) = d(total)/t(total)
So, r(average) = 20/(1/3 + 1/5).
After simplifying, we get:
r(average) = 37.5 mi/hr.
Explanation:hope this helps!!!