Question

if a speed of a car is decreased by 8km/hr ,it takes 1 hour more to cover a distance of 240km find the original speed of the car​

Answer 1

SolutioN :

• Time = 1 hr
• Distance = 240 km
• Decreased speed = (x - 8) km/hr

Let the original speed be x km/hr.

❍ According to Question now

→ Time = Distance/Time

→ 1 = 240/(x - 8) - 240/x

→ 1 = 240x - 240(x - 8)/x(x - 8)

→ 1 = 246 x - 246x + 1920/x² - 8x

→ x² - 8x = 1920

→ x² - 8x - 1920 = 0

By splitting middle term we get :

→ x² - 40x + 48x - 1920 = 0

→ x² - 48x + 40x - 1920 = 0

→ x(x - 48) + 40(x - 48) = 0

→ (x + 40) (x - 48) = 0

→ x = -40 or x = 48

The speed is never negative so 48 km/hr is the answer

Answer 2

${\huge{\underline{\underline{\bf{Question:-}}}}}$

if a speed of a car is decreased by 8km/hr ,it takes 1 hour more to cover a distance of 240km find the original speed of the car?

${\huge{\underline{\underline{\bf{Answer:-}}}}}$

Let s & t be the original speed & time taken.

So s×t = 240

t = 240/s

Also (s - 8)(t+1) = 240

st+s-8t-8 = 240

Applying the value of st & t in above equation

240+s-8×240/s-8 = 240

s -1920/s = 8

s²-1920 = 8s

s²-8s-1920 = 0

(s-48)(s+40) = 0

So s = 48 or -40

Since s can not be negative, s = 48

So original speed of the car is 48 km/hr.

${\huge{\underline{\underline{\bf{More\: information}}}}}$

➔$speed = \: \dfrac{distance}{time}$

➔ Speed is a scalar quantity.

$\huge{\underline{\sf{\Red{Thanks}}}}$