Question

an increase in speed of a car by 10km/hr saves 30mins in a journey of 100km.find the initial speed​

Answer 1

Answer:

speed=x

time =y

xy=100 y=100

Speeed = 40km/h

Answer 2

$\red{Given:-}$

Total distance, D = 715 Km

$\sf\small\red{To \: Find:-}$

Speed of the car

We know,

Let the speed of the car be x km/hr.

$speed = \frac{distance}{time}$

When the car travels at uniform speed, time taken =

$= \frac{715}{x} km .h$

If it travels at a speed of 10 km/hr more, time taken =

$= \frac{715}{x + 10} km.hr$

and the difference of time taken is 2 hrs, so the equation becomes

$\frac{715}{x} - \frac{715}{x + 10} = 2$

$= > \frac{715(x + 10) - 715x}{x(x + 10)} = 2$

$= 715(x + 10) - 715x = 2x(x + 10)$

$= > 715 0= 2x(x + 10)$

$= > 3575 = x(x + 10)$

$= > {x}^{2} + 10x - 3575 = 0$

$= > x(x + 65) - 55(x + 65) = 0$

$= > (x - 55)(x + 65) = 0$

$= x = 55.x = - 65$

As the speed cannot be negative, so speed of the train, x = 55 km/hr