Question

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Answer 1

Step-by-step explanation:

Total distance = 780 km

Let the distance covered by car be x km.

then, distance covered by train is ( 780 - x) km.

Now, speed of car = 60 km/h.

and you know distance covered = x km

you easily find the time taken to cover this 'x' km by the car using relation:

[ time = distance / speed ]

Time taken by car

Time taken by car = distance covered by car / speed of car

Time taken by car = distance covered by car / speed of car = x km / 60 km/h

Time taken by car = distance covered by car / speed of car = x km / 60 km/h= (x/60) h (* maintain units)

similarly, speed of train = 100 km/h

Time taken by train

Time taken by train= distance covered by train / speed of train

Time taken by train= distance covered by train / speed of train = (780 - x) km / 100 km/h

Time taken by train= distance covered by train / speed of train = (780 - x) km / 100 km/h= {(780 - x) / 100 } h

now, we know that

total time = 9 h

we just have to add both the car's time and train's time.

we get:

(Time taken by car)+(Time taken by train) = 9 h

(x/60) h + {(780 - x) / 100 } h = 9 h

After taking LCM you will get:

5x + 2340 - 3x = 300 ×9

=> 2x = 360

=> x = 180.

Now we just have to substitute x:

Time taken by train. = {(780 - x) / 100 } h

= (780-180) / 100 h

= 600 / 100 h

= 6 h

Distance covered by train = ( 780 - x) km

= ( 780 - 180) km

= 600 km

Required time = 6 h

Required distance = 600 km.