Question

There are three places P, Q and R on the bank of
a river. Q is just at the midway between P and R.
A boat can go from P to Q and back in 5 hours 15
minutes. The boat takes 7 hours to go from P to
R. How long would it take to return from R to P?​

Answer 1

Answer:

12 hour15second_________________

Answer 2

Answer:

3.5 hours or 3 hours 30 mins

Step-by-step explanation:

Since Q is mid way between P and R,

PQ=QR= d (assume)

Given,

Assuming P-Q-R as Upstream,

Time taken from P to R, i.e., 2d dist upstream = 7 hours

Therefore, Time taken from P to Q, i.e., d dist in the same direction = 7÷2 = 3.5 hours.

Assuming R-Q-P as Downstream,

Given,

Time taken from P to Q and back from Q to P = 5 hours 15 mins = 5.25 hours

Therefore, time taken from Q to P, d dist Downstream = 5.25-3.5 = 1.75 hour

Now, time taken from R to P, i.e., 2d dist same direction = 2x(time taken for d dist in the same direction)

= 2x1.75 hours

= 3.5 Hours or 3 hours 30 mins.