Mensa question....what the?

[Road2Ruin]

A colleague of mine has a Mensa calendar with a question every day. The latest question though has us both baffled even though we have looked up the answer. I pose this question to the P&P massive to see how to do it or have Mensa just screwed up and not supplied enough info?

'A car completes its outward journey at a speed of 42mph. Due to mecganical problems it returns, over excatly the same distance, at only 21mph. What is the car's average speed over the entire journey?

If you say 31.5mph aparantely you are wrong.

Any other suggestions?

I do have the answer they give but cant see how they got to it without further info.

Pete

[G'kar]

28 mph?

[convert]

I'm with him 28mph.

[Nobody You Know]

I got 28mph average.

[XJSJohn]

33?

not gud wiv numbers when ah run outa fingers an' toes ....

[OJ]

28mph

Spends twice as long doing 21 as 42. Average speed is total distance over total time taken, time taken is 3 hours not 2

[dan101smith]

21mph

[Arese]

Is it this years or last years? I have last years, so could check my answers for you if you tell me the date.

[Tyre_Tread]

28mph

If it travels for one hour, the distance travelled at 42 mph would be 42 miles and therefore the round trip is 84miles. It takes twice as long (2 hours) for the reurn journey as for the outward journey and therefore divide the total distance travelled by 3 (hours) 84/3= 28.

[Nobody You Know]

Assume the first journey takes exactly 1 hour then the car travels 84 miles in 3 hours.

84/3 = 28mph average

[spikeyhead]

If the journey is 42 miles then its spent one hout travellign at 42mph
and two hours travelling at half that speed.

Thicko

[Mrs Grumpy]

28 mph?

[Davi]

say it does 42mph for one hour, it's covered 42 miles.

to return, at 21mph, it takes 2 hours.

Total distance covered = 84 miles, total time taken = 3 hours

average = 28mph

feck - the mind is willing, the fingers are tooooo slow

Edited by Davi on Wednesday 28th January 11:23

[gamefreaks]

I get 28Mph too.

This is because it took twice as long to get back!

[Fuzzy Wuzzy]

OJ said:

28mph

Spends twice as long doing 21 as 42. Average speed is total distance over total time taken, time taken is 3 hours not 2

[Triumph Coupe]

dan101smith said:

21mph

I'm with him. 21 1/3 mph

[G'kar]

Plotloss said:

dan101smith said:

21mph

Thats what I thought.

If the car travels for 1 hour it has gone 42 miles.

If then has to return 42 miles at 21mph which takes two hours.

63 miles in 3 hours is an average speed of 21mph

Quoted for incredible denseness in the full knowledge you can delete it.

42+42 = 63?

Your clients must love your expense claims

[mechsympathy]

Plotloss said:

If the car travels for 1 hour it has gone 42 miles.

If then has to return 42 miles at 21mph which takes two hours.

63 miles in 3 hours is an average speed of 21mph

It's an 84 mile round trip. The 63 mile point is half way home at 2 hours.

[Neil_H]

Plotloss said:

dan101smith said:

21mph

Thats what I thought.

If the car travels for 1 hour it has gone 42 miles.

If then has to return 42 miles at 21mph which takes two hours.

63 miles in 3 hours is an average speed of 21mph

Why 63 miles? The return journey is just as far.

[Triumph Coupe]

Triumph Coupe said:

dan101smith said:

21mph

I'm with him. 21 1/3 mph

No i'm not! I can't divide 84 by 3 in my head! Idiot!