A man goes down stream with a boat to some destination and returns upstream to his original place in 5 hours. If the speed of the boat in still water and the strean are 10km/hr and 14km/hr respectively, the distance of the destination from the string place is
Choose the most appropriate option
A) 11 km B) 71 km C) 21 km D) 41 km E) 91 km
Explanation:   Let the distance covered be D km.   \inline \frac{D}{10+4}+\frac{D}{10-4}=5   \Rightarrow \frac{D}{14}+\frac{D}{6}=5   \inline \Rightarrow 10D= 42\times 5=210   \inline \Rightarrow D= 21 km   Answer: 21 km
<result>C</result>
A man goes down stream with a boat to some destination and returns upstream to his original place in 5 hours. If the speed of the boat in still water and the strean are 10km/hr and 14km/hr respectively, the distance of the destination from the string place is