Question

An aeroplane take 1 hour less for a journey of 1200 km if its speed is increased by 100 km/hrs from its usual speed. find the usual speed​

Answer 1

Let original speed be x.


time = distance/speed


original time = 1200 / x


new time = 1200 / x+100


1200 / x - 1200 / x + 100 = 1


1200  (1 / x - 1 / x + 100)=1


1200 (x + 100 - x / x* +100x) =1                   here x* is x square.


120000 = x * + 100x


x * + 100x -120000 =0


therefore by solving equation  


x = 300 km/hr

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Answer 2

HEY MATE!

HERE IS YOUR ANSWER:

Let the usual speed be xkm/hr

distance=1200

time1 =1200/x

time2=1200/x+100

now, 1200/x-1200/x+100=1

1200(x+100)-1200x/x(x+100)=1

1200x+120000-1200x/x^2+100x=1

120000=x^2+100x

0=x^2+100x-120000

0=x^2+400x-300x-120000

0=x(x+400)-300(x+400)

0=(x-300)(x+400)

x=300,-400

Speed cannot be negative,

Hence the usual speed is 300km/hr

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HOPE IT HELPED ^_^