Question

Speed of a car is 'x' km/hr & it takes 'y' hrs to cover a certain distance. If it's speed is increased by 5 km/hr , it will take 4 hrs less to cover same distance". This condition is represented by equation ____

 4x - 5y + 20 = 0  

5y - 4x + 20 = 0

 None of these

 (x + 5)(y - 4) = 20​

Answer 1

Answer:

option D

Step-by-step explanation:

In question x is changed as x+5 and y is changed as you therefore (x+5)(y-4) =20

Answer 2

Given: Speed of car = $x$ km/h

           Time taken by it to cover a certain distance = $y$ hours

           If, speed increased by 5 km/h, time will decrease by 4 hours

To find: An equation that will represent given condition

Solution: According to the given condition,

Initial speed of the car = $x$ km/h

Time taken by it to cover a certain distance = $y$ hours

Using Speed formula:

.: Speed = $\frac{Distance}{Time}$

.: Distance = Speed x Time

                  = $x$ x $y$

 Distance  = $xy$ km                       ...(1)

Now, it's also given that if speed is increased by 5 km/h then it will take 4 hours less to cover the same distance

New speed = $(x + 5)$ km/h

New time = $(y - 4)$ hours

.: Distance = Speed x Time

Distance = $(x + 5)$ x $(y - 4)$           ...(2)

Comparing equation (1) and (2) as distance is same

⇒ $xy = (x + 5)$ x $(y - 4)$

⇒ $xy =$ $x (y - 4) + 5 (y - 4)$

⇒ $xy$  = $xy - 4x + 5y - 20$

⇒ $xy - xy + 4x - 5y + 20 = 0$

⇒ $4x - 5y + 20 = 0$

The required equation is $4x - 5y + 20 = 0$