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Once: win one of two Mensa Brain Trainer hand held consoles

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Found 19th Sep 2009
this ones a good tester

A helicopter covers its outward journey at 322 mph.
It returns, over exactly the same distance at 241.5 mph
What is the helicopters average speed over the entire journey?

For a chance to win one of two Mensa Brain Trainer hand held consoles, simply e-mail the correct answer together with your full name and address to the Puzzle Editor

I make the answer 2*(241.5*322)/(241.5+322) = 276mph.

7 Comments

surely you just add both and then divide by 2?
i make it 281.75

entered, thanks

wow, that took all of 2 seconds.
try this one
If birmingham is 26 miles from your position, burnley is 50 miles, bradford is 8 miles. How far is blackpool?

brooke007bond;6337493

Hi, I believe the answer is 281.75to find the average speed you add the … Hi, I believe the answer is 281.75to find the average speed you add the two speeds then divide by two.322 + 241.5 = 563.5, 563.5 / 2 = 281.75thanks, heat added



That's the common mistake people make with this sort of problem. Speed=distance/time (s=d/t). You can rearrange the equation to t=d/s

For the outward journey, the time taken is equal to 322/distance. On the return journey, the time taken is equal to 241.5/distance. This makes the total time of the journey 322/d + 241.5/d. If the total distance travelled on the journey is 2d, the average speed is 2d/[(322/d)+(241.5/100)] = 276mph

Can anyone give me the e'mail address of the Puzzle Editor, my laptop will not open a direct link

Thanks
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