Question

A boat takes 2 hours to travel 8km and back in still water lake.With water velocity of 4 kmph the time taken for going upstream of 8km and coming back is.

• A. 160 minutes
• B. 80 minutes
• C. 320 minutes
• D. 180 minutes

Answer 1

Answer: (A)

160 minutes

Answer 2

$V_B = \frac{8 + 8}{2} = 8 kmph$ $t = t_1 + t_2 = \frac{8}{\nu_B + \nu_r} + \frac{8}{\nu_b - \nu_r} = 160 min$