Brain teaser...
A plane maintains an average speed of 696mph from London to New York. It then returns from New York to London at an average speed of 145mph. What is the average speed for the entire journey?
overyourhead - some irreverent musings by a gay London guy - crawling though technology, love and life... so you don't have to.
average speed = 240 mph
ReplyDeleteCorrect!
ReplyDeleteHow's that, then? -confused
ReplyDeleteDistance = speed x time
ReplyDeleteAverage speed over = s1 = 696
Average speed back = s2 = 145
So if time over is t1 and time back is t2 then distance = s1 x t1 = s2 x t2
Total average speed = (2 x distance)/(t1 +t2) = (2 x s2 x t2)/(t1 + t2) = (2 x s2)/(t1/t2 + 1) = (2 x s2)/(s2 / s1 + 1) = (2 x s2 x s1)/(s2 + s1) = (2 x 145 x 696)/(145 + 696) = 240