Question

.A plane left 40 minutes late due to bad weather and in order to reach its destination,

1600 km away in time, it had to increase its speed by 400 km/hr from its usual speed.

Find the usual speed of the plane​

Answer 1

Let the original speed be = x km / hr

we know that : time =speeddistance

As all the things are in hours (unit) we need to correct time in hours unit.

6040=32 hours

According to the question, x1600−x+4001600=32

(x)(x+400)1600x.640000−1600x×32

1920000=2x2+800x

2x2+800x−1920000=0

2(x2+400x−960000)=0

x2+400x−960000=0/2

x2+400x−960000=0

x2+1200x−800x−960000=0

x(x+1200)−800(x+1200)=0

(x−800)(x+1200)=0

x=80