# math

an express train makes a run of 240 km at a certain speed. another train whose speed is 12km/hr less takes an hour longer to cover the same distance. find the speed of the express train in km/hr.

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1. speed of express ---- x km/h
speed of slow train -- x - 12 km/h

solve for x

240/(x-12) - 240/x = 1

(saying: the difference in their times = 1 hr
and time = distance/rate )

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2. v t = 240 so t = (240/v)

(v-12) (t+1) = 240
====================

v t - 12 t + v - 12 = 240
or
v + vt -12 t = 252
substitute
v +240 - 12(240/v) = 252

v^2 - 12 v - 2880 = 0

(v-60)(v+48) = 0
v = -48 simply will not do
so
v = 48 km/hour

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3. 60 km/hour

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4. How can it be 48 ,it must be less than the other train

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5. I donot understand

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6. Even now i donot understand

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7. Ya the answer is right u can check it

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8. Ya that's right u all can check it

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