<PRE><B>Question 728903</B>
Monday
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Toronto to Montreal time = distance / speed = 540/x

Round trip 540/x + 540/x
= 1080/x...................(1)



Friday

wind speed = 80 km/h
with wind time = 540/(x+80)

Against wind time = 540/(x-80)

Total time = 540/(x+80)+540/(x-80)

540(x-80)+540(x+80)/ (x+80)(x-80)= time for round trip

Simplify

1080x/((x+80)(x-80)= time.................(2)

Since the numerator is same and the denominator is bigger  in (2) time taken is less on Friday for the round trip</PRE>