A train starts running with the initial speed of 40 km/hr, with its speed increasing every hour by 5 km/hr. how many hours will it take to cover a distance of 460 km?
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in 1st hour covers 40 km then increase by 5 every hour.
so series in a.p.
where a=40 d=5 &s=460
s=n/2{2a+(n-1)d}
460=n/2{80+5n-5}
920=75n+5n^2
n^2+15n-184=0
(n+23)(n-8)=0
but n is always positive
so n=8
so series in a.p.
where a=40 d=5 &s=460
s=n/2{2a+(n-1)d}
460=n/2{80+5n-5}
920=75n+5n^2
n^2+15n-184=0
(n+23)(n-8)=0
but n is always positive
so n=8
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