79. In a flight of 600 km, an aircraft was slowed down due to bad weather.
The average speed of the trip was reduced by 200 km/br and the time of
flight increased by 30 minutes. Find the duration of flight,
points A 3. 4) and
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Answer:
ANSWER
Let the original speed of the aircraft be x km/hr.
then new speed =(x−200) km.hr
Duration of flight at original speed =(
x
600
)hr
Duration of fight at reduced speed =(
x−200
600
)hr
∴
x−200
600
−
x
600
=
2
1
⇒
x(x−200)
600x−600(x−20)
=
2
1
⇒
x
2
−200x
120000
=
2
1
⇒x
2
−200x−240000=0⇒x
2
−600x+400x−240000=0
⇒(x−600)(x+400)=0⇒x=600orx=−400⇒x=600
So, the origianl speed of the aircraft was 600km/hr
hence, duration of flight =(
x
600
)hr=(
60
600
)hr=1hr
so, your answer is 1 hr
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