Question

A boat takes 4 hours to go 44 km downstream and it can go 20 km
same time. Find the speed of the stream and that of the boat in still
water.​

Answer 1

Answer:

Speed of boat = 8km/ hr

Speed of strem = 3km/ hr

Solution =》

Let the speed of the stream = xkm/hr

Let The speed of the boat in still water = y km/ hr

Downstream

$x + y = \frac{44}{4} \\ = x + y = 11.........(1)$

Upstream

$x - y = \frac{20}{4} \\ = x - y = 5.........(2)$

Adding eq 1 and eq2

x + y = 11

x - y = 5

——————

2x = 16

x = 16/2

x = 8

putting value of x in eq 1

x+y =11

8+y=11

y=11-8

y=3

So, Speed of Strem = 8km/ hr

Speed of boat in the still water = 3km/ hr

Answer 2

Answer:

• Speed of stream = 3 km/h
• Speed of boat in still water = 8 km/h

Step-by-step explanation:

Let the speed of stream be y km/h and boat be x km/h.

✏ Downstream:

Distance = 44 km

speed = (x + y) km/h

∴ time, $\rm{t_1}$ = distance/speed = 44/x + y

i.e., 4 = 44/x + y

∴ x + y = 11 → (1)

$\hrulefill$

✏ Upstream:

Distance = 20 km

speed = (x - y) km/h

time, $\rm{t_2}$ = 20/x - y

i.e., 4 = 20/x - y

∴ x - y = 5 → (2)

Now, (1) + (2) ⇒

⇝ 2x = 16

⇝ x = 16/2

⇝ x = 8

Substituting the value of x in (1) ⇒

⇝ 8 + y = 11

⇝ y = 11 - 8

⇝ y = 3

i.e., speed of stream = 3 km/h

speed of boat in still water = 8 km/h