Question

A plane left 30 minutes late than its scheduled time and in order to reach the destination 1000 Km away in time it had to increase its speed by 100 Km/h from the usual speed find its usual speed​

Answer 1

Let the usual speed of the plane be xkm/h

New speed = (X+100)km/h

Now , difference in time = 30min

= 1000/X -1000/(X+100) = 30/60

(because time = distance /speed)

= 1000|1/X -1/X+100 = 3/6

= 1000|X+100-x/X(X+100) = 3/6

= 100000/x^2+100x= 1/2

= 200000= x^2+100x

= x^2+100x-200000

now factorise it

= x^2+500x-400x-200000

= X(X+500) -400(X + 500)

= (x-400) = 0

and (X+500) =

we get

X = 400 and X= -500

speed can't be in negative

so

X=400km/h

answer

the usual

speed of the plane is

400km/h