Question

A train travelling at a speed of 6900 km. would have taken 9 hour less to travel to same distance if its speed were 15km/hour more. find the original speed of the train.

Answer 1

Answer:

Step-by-step explanation:

a train travelled a distance is 6900km with a time of x hour

if a train taken 9 hour less mean x-9 hours

speed of train= 6900/x-9=15km

6900=(x-9)15

6900=15x-135

6900+135=15x

7035=15x

x=7035/15

x=469 hours

9 hour less means 460hour

original speed of a train 6900/469 = 14.7 km /hour

Answer 2

let original speed of train = x km/h

we know,

time = distance/speed

first case

———————

time taken by train = 360/x hour

second case

——————————

time taken by train its speed increase 5 km/h = 360/( x + 5)

question says that

time taken by train in first - time taken by train in 2nd case = 48 min = 48/60 hour

360/x - 360/(x +5) = 48/60 = 4/5

360{ 1/x - 1/(x +5) } = 4/5

360 ×5/4 { 5/(x² +5x )} =1

450 x 5 = x² + 5x

x² +5x -2250 = 0

x = { -5±√(25+9000) }/2

=(-5 ±√(9025) )/2

=(-5 ± 95)/2

= -50 , 45

but x ≠ -50 because speed doesn't negative

so, x = 45 km/h

hence, original speed of train = 45 km/h