Question

Samantha swam upstream for some distance in one hour. She then swam downstream the same river for the same distance in only 12 minutes. If the river flows at 4 mph, how fast can Samantha swim in still water? 3 mph 6 mph 7 mph 8 mph

Answer 1

B aka 6mph

Explanation:

Answer 2

The option B is correct, i.e. 6 mph.

Explanation:

Suppose Samantha swim in still water at speed of X mph.

If the river flows at 4 mph,

Then Upstream speed = (X-4) mph.

And Downstream speed = (X+4) mph.

Samantha swam upstream for some distance in one hour. She then swam downstream the same river for the same distance in only 12 minutes.

It means Distance upstream = Distance downstream.

Speed upstream x Time upstream = Speed downstream x Time downstream.

(x-4) * 1 = (x+4) * 12/60

x - 4 = 0.2x + 0.8

x - 0.2x = 0.8 + 4

0.8x = 4.8

x = 4.8/0.8 = 6 mph.

Hence, the option B is correct, i.e. 6 mph.