Little puzzle for petrol heads

[RSTDL]

A race car goes around a one mile long oval circuit.

It averages 30mph for the first lap

What speed does it have to do the second lap in to average 60mph FOR BOTH LAPS?

One for you captain.....lol



Come on lets see whos clever - oh and its not the obviuos answer of......?

Let mes know when yousa wan the answer.....

 

[Captain Slarty]

math is not my strong point lol..



however, if the total distance is 2 miles (2 laps of 1 mile each) we need a total time of 120 seconds for the 2 laps (2 mins) to average 60 mph (1 mile in 60 secs)

as the first lap has taken 2 mins... we cant do it.. all our alloted time has been used up... ie - it took 120 secs for the first lap.. so no time left.

Joe..

 

[Matt - Leics]

90mph... Hope you arent going to make me look daft now!

 

[hype]

Its making my head hurt thinking about it but I think it would be 0 mph.

 

[RSTDL]

all wrong!!!!!

Answer anyone?

 

[viceroy]

120mph?

 

[KeithO]

30mph??

 

[hype]

Its impossible isnt it. Literally I mean. No matter how fast you go u cant do it.

 

[RSTDL]

All wrong - thing about time not distance it takes to each lap (NOTE THE WORD AVERAGE) were not taking into account the time it takes to accelerate from 30mph to ? Its the average for both laps is 60mph!

Think how long it takes to average 30mph for 1 lap then how long it would take to average 60mph for 2 laps........then try again

 

[Stu_H]

An infinate speed.

 

[Stu_H]

You do the first lap in 2mins (1/30=0.0333hrs = 2mins)

To do 2 miles at 60mph youll need to do it in 2 mins, but 2 mins is already up.



Stu.

 

[hype]

Stu_H is right, its an infinite speed; therefore its impossible to calculate.

 

[RSTDL]

90 mph is wrong. So is 72 mph. Or any other answer.....





----


To average 60 mph (1 mile/min.), you must drive two laps (2 miles) in 2 minutes.





Lap 1 at 30 mph (2 mins/mile) takes you two minutes. Therefore, to average 60 Mph, you must finish the second lap in 0 minutes.


(So you cant do it unless you travel at infinite speed.)








[aside, for information only]





If we drive 90mph in the second lap, 90mph = 1.5 miles per minute. So itll take 40 seconds to do the lap.



You would have taken a total of 2 minutes, 40 seconds to do both laps.



2:40 = 160 seconds. Divide by 2 and thats 80 seconds per lap.



Therefore:




One mile in 80 seconds = ave. speed (over both laps) of 45 MPH. (not 60mph)





[/side, for information only]

 

[Matt - Leics]

I seem to remember from maths there are about three different types of average.. mean, modal and something else. So Im right

IDST times infinity.

 

[viceroy]

Then the captain takes the prize as he got the answer right off

 

[hype]

Yeah, the captain was right.

 

[RSTDL]

Sorry Captain - u were actually right - oops - I posted me reply before urs had come up!!! soz and weell done

 

[Captain Slarty]

got me worried there for a min when you said I was wrong m8 !!.. thought me head had exploded... lol.



what do I win ??

Joe.

 

[Oakley]

iTS SOMETHIMG LIKE 210 MPH

YOU HAVENT GOT A CERTAIN TIME TO DO IT! IF YOU DID THE FIRST LAP AT 30 MPH THEN THE SECOND LAP AT 2000MPH THE THE AVERAGE WOULD BE GREATER THAN 60 !!! THINK ABOUT IT

 

[Oakley]

DONE IT!!

YOU WOULD HAVE TO DO THE SECOND LAP AT 7,500,000MPH THAT IS DOING THE SECOND LAP IN 0.00048 SECONDS. i KNEW IT WAS POSSIBLE, JUST HAD TO WORK IT OUT!!

 

[Captain Slarty]

that dont average 60 mph though...

you have only averaged 59.9856034551707590178357194273374 mph...

so, sorry, nope lol. !

 

[Oakley]

I was only joking, Got you thinking though and you had to work it out.

Didnt know I was that close!