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Question 54
A train takes 2 hours less for a journey of 300 km by increasing its speed by 5 km/h. What is its normal speed?
Solution
Time= distance/speed
let unusual speed be x
so (300/x)-(300/x+5)=2
300{(x+5)-x}=2(x+5)x
1500=2x(x+5)
x(x+5)=750
(x^2)+5x-750=0
from this equation, we can find the two zeroes for the equation as -30 and 25
as speed can never be negative,
so x=25 kmph
A is correct choice.
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