Question

Questions
3. Downstream speed of a boat is 5 km/hr more than its upstream speed and the speed of boat
in still water is 280% more than the speed of sream. Find the total time taken by boat to
travel 42 km in downstream and 31.5 km in upstream?​

Answer 1

$\Large\textsf{\underline{\underline{Solution :-}}}$

$\large\texttt{➛ Let the speed of the stream be ' x km / hr ' }$

$\large\texttt{➛ So , the speed of the boat}\\ \large\texttt{in still water will be :-}$

$\large\texttt{ ↦ 280 \% \: \: of \: \: x }$

$\large\texttt{ ↦ \cancel\cfrac{ 280}{100} × x }$

$\large\texttt{↦ 2.8 x }$

$\large\texttt{➛ So , the speed of boat }\\ \large\texttt{in still water = \boxed{2.8x + x }}$

$\large\texttt\textcolor{red}{\: \: \:\: \: \: \: \: \:\: \: \: \: \: \:\: \: \: \: \: \:\: \: \: \: \: \:\: \: \: \: \: \: \: \: \:\: \: \: \boxed{= 3.8x \: \: km \: / \: hr}}$

• Speed of the boat upstream will be = Speed of the boat in still water - Speed of the Stream .

Answer 2

Answer:

Time taken by boat to travel 42km downstream is 3.5hr

Time taken by boat to travel 31.5km upstream is 4.5hr

Step-by-step explanation:

Given that,

Down stream speed of the boat is 5 km/hr more than its upstream speed and the speed of boat in still water is 280% more than the speed of steam. We  need to find the total time taken by boat to travel 42 km in downstream and 31.5 km in upstream.

Let the speed of the boat in still water be x km/h and the speed of the stream be y km/h

Therefore,the speed of the boat downstream is (x+y)km/h and

The speed of the boat upstream is (x-y)km/h

According to the given question,we have $x+y=x-y+5= > y=2.5km/h$

Also given that,

$x=y+\frac{280}{100} y= > x=3.8y=3.8\times2.5=9.5km/h$

Therefore,time taken by boat to travel 42km downstream is $\frac{42}{2.5+9.5} =3.5hr$

and the time taken by boat to travel 31.5km upstream is $\frac{31.5}{9.5-2.5} =4.5hr$

#SPJ3