Question

A boat goes at a speed of 30 kmph in still water. What time does it take to travel 50 kms upstream and then 70 kms downstream in water of speed 5 kmph?

• A. 2
• B. 4
• C. 6
• D. 8

Answer 1

Answer:

B. 4

Speed of Stream $S_s=5km/hr$

Speed of Boat $B_s = 30 km/hr$

Upstream Speed,$U_s= 30-5=25km/hr$

Downstream Speed,$D_s=30+5=35km/hr$

$$Time taken to travel 50km upstream and 70km Downstream is,

$=\frac{50}{25}+\frac{70}{35}$

$=2+2$

$=4 hours$