A car travel 100 km. if speed increased by 10 km it saves 30 min. what is the initial speed of the car
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let the speed of the car be x
time taken to cover 36 km = 36/x hr
ATQ
36/x - 36/(x+10) = 18/60
(36(x+10) - 36x)/x(x+10) = 3/10
(36x + 360 - 36x)/(x^2+ 10x) = 3/10
360x10 = 3(x^2 + 10x)
3x^2 + 30x = 3600
3x^2 + 30x - 3600= 0
x^2 + 10x - 1200=0
x^2 + 40x - 30x - 1200=0
x(x+40) - 30(x+ 40)= 0
(x-30)(x+40)=0
we get 2 answers
But x=30 is the correct one
therefore the speed of the car is 30 km/hr
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