Mai is kayaking on a river that has a current of 2 miles per hour. If r represents her rate in calm water, then (r + 2) represents her rate with the current, and (r – 2) represents her rate against the current. Mai kayaks 2 miles downstream and then back to her starting point. Use the formula for time,
t
=
d
r
t=
r
d
​
, where d is the distance, to write a simplified expression for the total time it takes Mai to complete the trip.


4
(
r
+
2
)
(
r
−
2
)
h
o
u
r
s
(r+2)(r−2)
4
​
hours

4
r
(
r
+
2
)
h
o
u
r
s
(r+2)
4r
​
hours

4
r
(
r
+
2
)
(
r
−
2
)
h
o
u
r
s
(r+2)(r−2)
4r
​
hours

4
(
r
−
2
)
h
o
u
r
s
(r−2)
4
​
hours