Question

A motor boat takes 2 hrs to travel a distance 9 km down the current and it takes 6 hrs to travel the same distance against the current.The speed of the boat in still water and that of the current respectively are:a. 3,1.5 b.3,2 c. 3.5,2.5 d.3,1

Answer 1

Step-by-step explanation:

answer: a.) 3,1.5

speed=distance coveredtime taken

Let us find out the speed of the boat upstream and downstream by the help of a problem statement.

Let us find out upstream speed:

⇒upstream speed=distance coveredtime taken⇒upstream speed=9km6hr⇒upstream speed=1.5km/hr

Now, let us find out downstream speed:

⇒downstream speed=distance coveredtime taken⇒downstream speed=9km2hr⇒downstream speed=4.5km/hr

As we know that the formula for the speed of the boat in the still water is given by:

⇒speed of the boat=upstream speed+downstream speed2

Now let us substitute the value of the upstream speed and the downstream speed in order to find the speed of the boat.

⇒speed of the boat=4.5+1.52km/hr⇒speed of the boat=62km/hr⇒speed of the boat=3km/hr

Also we know that the formula for the speed of the current in terms of upstream and downstream speed is given by:

⇒speed of the current=downstream speed−upstream speed2

Now let us substitute the value of the upstream speed and the downstream speed in order to find the speed of the current.

⇒speed of the current=4.5−1.52km/hr⇒speed of the current=32km/hr⇒speed of the current=1.5km/hr

Hence, the speed of the boat in the still water is 3 km/hr and the speed of the current is 1.5 km/hr.

Answer 2

Option A > 9/v+s=2 & 9/v-s=6
V+s= 9/2 & v-s= 3/2 forming 2 equations