Question

a train covers a distance of 600 km had the speed been 20 km/hr have more then time taken to cover the distance would have been reduced by 5 hrs solve the equation in and to evaluate x?​

Answer 1

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Given s=600km, v=x km/h

Now, t= s/v= 600/x

=>tx= 600 -> (i)

Again, (t-5)=600/(x+20) [Using (i)]

=>(t-5)(x+20)=tx

=>tx+20t–5x-100=tx

=>20t–5x-100=0

=>20(600/x)-5x-100=0 [As t=600/x]

=>12000–5x^2–100x=0

=>x^2+20x-2400=0

=>x={-20+√(400+9600)}/2

or x={-20-√(400+9600)}/2

=>x={-20+100}/2

or x={-20–100}/2

Thus, x=40 km/hr

or x=-60 km/hr (not applicable here)

[ Formula used to find the roots of a quadratic equation (ax^2+bx+c=0) is

x={-b+√(b^2–4ac)}/(2a)

and x={-b-√(b^2–4ac)}/(2a) ]