A plane left 30 minutes less than its schedule time and in order to reach the destination 1500km away in time ,it had to increase it's speed by 100km/h from the usual speed.find usual speed
Parul678:
i also want to know
It's 500 km/h.
let the speed of plane be x now, atq : we get that 1500/x-1500/x+100=1/2.....(changing 30 mins in form of hr to get 1/2) =1500(x+100)-1500/x^2+100x=1/2 =1500x+150000_1500x/x^2+100x=1/2 =150000*2=x^2+100x =300000=x^2+100x =x^2+100x-300000=0 ;by middle term splittig we get that =x^2+600x-500x-300000=x(x+600)-500(x+600) =;(x+600)(x-500) =;x=-600, x =500 neglecting -ve value of x we get speed as 500 km/hr this is what i did in yesterdaysxam hope it would hep u as well..
Thnx frnd and also do ur best in RETEST....
yaah ahn ahn i wish it will go best
Answers
Answered by
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Let the usual speed be x km/hr
Then ,time taken by train to cover 1500km= 1500hr/x
If its speed is increased by 100km/hr
Then new speed is =(x+100)km/hr
Time taken by train to cover 1500km=1500hr/x+100
A/q
1500/x=1500/x+100 -1/2
1500/x+100-1500/x=1/2
By solving this equation we get the usual speed of the train=500km/hr
Then ,time taken by train to cover 1500km= 1500hr/x
If its speed is increased by 100km/hr
Then new speed is =(x+100)km/hr
Time taken by train to cover 1500km=1500hr/x+100
A/q
1500/x=1500/x+100 -1/2
1500/x+100-1500/x=1/2
By solving this equation we get the usual speed of the train=500km/hr
Answered by
0
Given:
Late = 30 min
Distance = 1500 km
Speed increase = 100 km / hr
To find:
The usual speed.
Solution:
By formula,
Speed = Distance / Time
Since the time is unknown,
Consider x for time,
Speed original = 1500 / x
Time taken = ( x - 1 / 2 )
Therefore,
Substituting the value of x,
Speed new = 1500 / (x - 1/2)
Speed New - Speed original = 100
( 1500 / ( x - 1 / 2 ) ) - ( 1500 / x ) = 100
150 ( ( 10 / x - 1 / 2 ) - 10 / x = 100
30 x -30 x +15 = 2x^2 - x
15 = 2x^2 - x
2x^2 - x -15 = 0
Solving,
x = -5/2
x = 3
As time cannot be negative,
The usual time taken by the plane is 3 hr
Speed original = ( 1500 / 3 ) = 500 km / hr
Hence, the usual speed of the plane is 500 km / hr
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