A motorboat whose speed is 18 km/hr in still water takes 1 hr more to go 24 km upstream
Answers
Explanation:
Given :
The speed of the motor bike instill water is 18 kmph,
It takes 1 hour to travel upstream & return to same spot,.
From this information we can say that,
⇒ The speed of motor boat (boat's engine) = 18 kmph ,
⇒ It traveled 24 km upstream & 24km downstream in 1 hour
We know that,
time = distance/time
So,
Let the speed of stream be x,
Then,
we can say that,
⇒ -x² - 48x + 324 = 0
⇒ x² + 48x - 324 = 0
⇒ x² - 6x + 54x - 324 = 0
⇒ x (x -6) + 54(x - 6) = 0
⇒ (x + 54)(x - 6) = 0
For the equation to be 0,
Either,
⇒ x + 54 = 0 (or) x - 6 = 0
⇒ x = -54 (or) x = 6
⇒ x = 6 (As speed can't be negative, x ≠ -54)
∴ The speed of the stream is 6 kmph
Hope it helps you.
Let the speed of the stream be x km\hr.
The speed of the boat upstream = (18 - x) km/hr
The speed of the boat downstream = (18 + x) km/hr
Distance = 24 km
As given in the question,
Time for upstream = 1 + Time for downstream
24/(18 - x) = 1 + 24/(18 + x)
24/(18 - x) - 24/(18 + x) = 1
x2 + 48x - 324 = 0
(x + 54)(x - 6) = 0
x ≠ - 54 as speed cannot be negative.
x = 6
The speed of the stream = 6 km/hr