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Can't fathom out how MENSA came to this answer.....
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I am struggling to work out how MENSA came up with an answer of 472mph to this question.........
An aeroplane covers its outward journey at 590mph. It returns, over exactly the same distance, at 393.33 mph. What is the plane's average speed over the whole journey?
Would anybody care to explain please?
An aeroplane covers its outward journey at 590mph. It returns, over exactly the same distance, at 393.33 mph. What is the plane's average speed over the whole journey?
Would anybody care to explain please?
Answers
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For more on marking an answer as the "Best Answer", please visit our FAQ.On a journey each way of 23206.47miles the outward journey would take 393.33 hours. The return journey would take 590 hours. The total time is 983.33hours. The total of both journeys is 46412,94 miles. Average speed is 46412.94/983.33 which gives 472.
Norberto, Vagrant and Mensa are perfectly correct!
Norberto, Vagrant and Mensa are perfectly correct!
It has finally sunk in!!!
Using similar figures and Norberto's method;
Distance to travel 12000 miles.
Outward speed, 600mph,
Inward speed, 400mph.
Outward = 12000/600 = 20.
Inward = 12000/400 = 30.
Total journey = 2x, so 12000 x 2 = 24000.
24000 / (20 + 30) = 24000 / 50 = 480.
I just couldn't see the way to solve this one myself! You learn something every day!
Using similar figures and Norberto's method;
Distance to travel 12000 miles.
Outward speed, 600mph,
Inward speed, 400mph.
Outward = 12000/600 = 20.
Inward = 12000/400 = 30.
Total journey = 2x, so 12000 x 2 = 24000.
24000 / (20 + 30) = 24000 / 50 = 480.
I just couldn't see the way to solve this one myself! You learn something every day!
Any problem designed to determine IQ is primarily designed to determine the ability to recognise relationships. The application of knowledge (mathematics, physics, geometry, language etc.) to the recognised relationship is secondary to the purpose of measuring intelligence.
The failure to recognise a relationship leads to the inability to resolve the facts.
The relationship ... 590 and 393.33 - mmm! That's about 1200 (2x600,3x400 - knowledge), but I see it is 2x10 and 3x6.66 less. The big clue comes from the glaringly obvious 393.33 borne of the knowledge that it must be the result of dividing by three (or a multiple of 3)
Now then the SIMPLE maths, without even knowing what you are trying to calculate, what else goes into 1180 ... that'll be 5 at a guess. Two lots of 1180 (2360) divided by 5 is 472 whatever-they're-called ... and five is the sum of the factors 2 and 3 (intelloigent assumption not proof).
Double check (for those without confidence). 4 lots of 1180 (2 journeys would have to be divided by 10). That wouldn't be 4720 thingies, would it? Simple maths, again!
The failure to recognise a relationship leads to the inability to resolve the facts.
The relationship ... 590 and 393.33 - mmm! That's about 1200 (2x600,3x400 - knowledge), but I see it is 2x10 and 3x6.66 less. The big clue comes from the glaringly obvious 393.33 borne of the knowledge that it must be the result of dividing by three (or a multiple of 3)
Now then the SIMPLE maths, without even knowing what you are trying to calculate, what else goes into 1180 ... that'll be 5 at a guess. Two lots of 1180 (2360) divided by 5 is 472 whatever-they're-called ... and five is the sum of the factors 2 and 3 (intelloigent assumption not proof).
Double check (for those without confidence). 4 lots of 1180 (2 journeys would have to be divided by 10). That wouldn't be 4720 thingies, would it? Simple maths, again!
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