Question

Maths
ch. 4
plz tell how to solve it

Answer 1

speed=distance/time
300/2=
150km/h
speed increase in 5km/h=
150*5=750km

Answer 2

Answer:

25 km/hr

Step-by-step explanation:

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

(i)

Let initial speed = x km/hr.

Distance = 300 km.

∴ Time = Distance/Speed

           = 300/x.

(ii)

Given that Speed is increased by 5 km/hr.

So, Speed after increasing = (x + 5) km/hr.

Distance = 300 km.

∴ Time = Distance/Speed

           = 300/(x + 5).

According to the given condition,

⇒ (300/x) - (300)/x + 5 = 2

⇒ [300(x + 5) - 300x]/x(x + 5) = 2

⇒ 300x + 1500 - 300x = 2[x(x + 5)]

⇒ 1500 = 2[x² + 5x]

⇒ 1500 = 2x² + 10x

⇒ 2x² + 10x - 1500 = 0

⇒ x² + 5x - 750 = 0

⇒ x² + 30x - 25x - 750 = 0

⇒ x(x + 30) - 25(x + 30) = 0

⇒ (x - 25)(x + 30) = 0

⇒ x = 25, -30{Speed cannot be negative}

⇒ x = 25.

Therefore, usual speed of the train = 25 km/hr.

Hope it helps!