Answer :
Answer:
previous speed of the aeroplane is 500 km/hr
Step-by-step explanation:
Given: Distance covered by aeroplane = 1500 km
It covers the same distance in a time which is half an hour less than the previous time if the speed is increased by 100 km/hr
To find: previous speed of the aeroplane
Solution:
Let x denotes the previous speed of the aeroplane.
Time taken by an aeroplane if speed is x km/hr = distance/speed = [tex]\frac{1500}{x}[/tex] hours
If speed is increased by 100 km/hr, new speed = (x + 100) km/hr
Time taken by an aeroplane if speed is (x + 100) km/hr = [tex]\frac{1500}{x+100}[/tex] hours
According to question,
[tex]\frac{1500}{x+100}=\frac{1500}{x}-\frac{1}{2}\\ \frac{1500}{x}-\frac{1500}{x+100}=\frac{1}{2} \\\frac{1}{x}-\frac{1}{x+100}=\frac{1}{3000}\\ \frac{x+100-x}{x(x+100)}=\frac{1}{3000}\\ x^2+100x=300000\\x^2+100x-300000=0\\[/tex]
[tex]x^2+600x-500x-300000=0\\x(x+600)-500(x+600)=0\\(x-500)(x+600)=0\\x=500\,,\,-600[/tex]
As speed can not be negative, [tex]x=-600[/tex] is rejected.
So,
previous speed of the aeroplane is 500 km/hr