Question

A man travels a certain distance at an average speed of 63km / h and baggage returns at an average speed of 42km / h, so what was the average speed of the car in the entire journey

एक आदमी एक निश्चित दुरी 63km / h कि औसत चाल जाता है तथा सामान दुरी 42km / h कि औसत चाल से वापस आता है तो पूरी यात्रा में गाड़ी कि औसत चाल क्या रही ​

Answer 1

Answer:

Let the speed of the train is Xkm/h

Time taken to cover 63km with X km/h speed is :

T1= Distance/SpeedT1=63/X hours---------(1)

It's given that train Travels a distance of 72 km at an average speed 6 km per hour more than its original speed.

Time taken to cover 72km with speed (x+6)Km/H

T2=72/x+6 hr------------(2)

But given that total time is 3hrs.T1+T2=3hrs

63/x+72(/x+6)=3taking 3 common,

21/x+24/(x+6)=121

(x+6)+24x=x(x+6)

21x+126+24x=x²+6x

x²+6x-45x-126=0

x²-39x-126=0

x²-42x+3x-126=0

x(x-42)+3(x-42)=0

(x-42)(x+3)=0

x=42, -3

since speed cannot be negative:x=42Km/h

∴Original speed of train=42km/h

Explanation: