daily express mensa teaser 23/05/12

[alison43331]

Hi

Please could someone shed some light on today's puzzle. The clue is as follows:

A car has travelled 150 miles at 40mph. It started its journey with eight gallons of fuel but its tank has been leaking throughout the journey and is now dry. The car completes 40 miles per gallon. How many gallons of fuel does it leak per hour?

Thanks

[glasman]

I make it 1.4 gallons lost per hour

[grasscarp]

I make it 2.13 gallons per hour.
The journey takes 3.75 hours. (150 miles at 40 mph)
You have lost 8 gallons in 3.75 hours.

[HowardKennitby]

I get 1.14 gal/hr

[glasman]

But, Grasscarp, you're not allowing for normal fuel usage on journey.

[grasscarp]

forget my solution. Fatally flawed! I was working on consumption, not leakage.

[Calibax]

I get 1.1333
Youve used 3.75 gallons driving so you've only LOST 4.25 gallons in 3.75 hours

[grasscarp]

Hangs head in shame and slinks away.

[elgreco]

I get 1 and 2/15ths gallons per hour

[alison43331]

Thanks for your help

Please can you explain how you get the answer 1.4 gallons per hour? I make it 2.13 gallons per hour. Thanks

[glasman]

Yes, you're right, Calibax. I subtracted 3.75 from 8 and got 5.25. Doh.

[Baldric]

Leaks 2.55 gallons per hour.

[HowardKennitby]

You start with 8 gal

You consume 3.75 gal in the engine leaving 4.25 gal lost through leakage.

Journey time is 3.75 hours

leakage rate is 4.25/3.75 = 1.1333 gal/hour

[Captain2]

Car uses a gallon every 40 miles so over 150miles uses 3.75 gallons.
Full tank = 8 galls less 'used' of 3.75 galls = 4.25 galls 'lost'
Journey takes 150 miles / at 40 mph = 3.75 hours

So 'loss' per hour = 4.25/3.75 = 1.13333 galls per hour

[Calibax]

You've used 3.75 gallons driving (150mi @ 40mpg = 150/40) in 3.75 hours (150mi @40mph = 150/40). You started with 8 gal so you've lost 8-3.75=4.25 gallons due to leakage. So leakage rate is 4.25 gal in 3.75 hours = 4.25/3.75 = 1.13333 gallons per hour

[alison43331]

Thanks so much...all is clear now!!!

[Baldric]

Now agree with Calibax, must get a calculator with BIGGER buttons
;o)

[Indepuss]

I get. 1,333R too.