Question

If speed of boat in still water and speed of current is 10 km/hr and 4 km/hr respectively. A boat moving from A to B (Point in a river) and come back to A. Total time taken in the whole journey is 20 hr; Find distance between A and B.

• A. 81 km
• B. 84 km
• C. 83 km
• D. 82 km

Answer 1

Answer:

B. 84 km

GIVEN:

Speed of boat in still water = 10 $\frac{km}{hr}$

Speed of current = 4 $\frac{km}{hr}$

FORMULAE USED:

Distance = Speed $\times$ Time

CALCULATION:

Total time taken in whole journey = 20hr

Speed of boat in upstream = 10 - 4 = 6 $\frac{km}{hr}$

Speed of boat in downstream = 10 + 4 = 14 $\frac{km}{hr}$

Let the distance from point A to B be "x"

20 = ($\frac{x}{6})$ + ($\frac{x}{14}$)

$\frac{5x}{21}=20$

x = 84

∴ Distance from point A to B is 84 km.