Question

please solve this: if the speed of an aeroplane is reduced by 40km/hr, it takes 20 minutes more to cover 1200km. Find the speed of the aeroplane.

Answer 1

Find the value of x...

x2-40x-144000=0
x2-400x+360x-144000=0
x(x-400)+360(x-400)=0
(x-400)(x+360)=0
x=400 or - 360
But speed cannot be negative so (- 360) is rejected and x=400

So, initially speed was :
400km/hr