Donald duck can can swim his pool downstream(with the pool current helping time) in exact 40 seconds and upstream(against the pool current) in a pool in exact 60 seconds. The length of pool is 2 kilometers.
How long Donald duck can cover distance of one side at a still pool (with no current).  Choose the correct answer:
A) 48 minutes.
B) 58 minutes.
C) 68 minutes.
D) 88 minutes.
E) 78 minutes.
Solution:   48 minutes.   Donald duck's speed = X km/seconds   pool current speed = Y km/seconds   2/(X+Y) = 40   2/(X-Y) = 60   Solving the simultaneous equations gives X = 1/24   Therefore, to cover 2km will take 2/X = 48 seconds   48 minutes.nswer 48 minutes.
<result>A</result>
Donald duck can can swim his pool downstream(with the pool current helping time) in exact 40 seconds and upstream(against the pool current) in a pool in exact 60 seconds. The length of pool is 2 kilometers.
How long Donald duck can cover distance of one side at a still pool (with no current).