Brain Teasers

[Cindy Ellis]

I guess we just read the problem differently. The way I read it, we were to choose between the two options...either change all of the suburbans' tires to the 13 mpg type, OR modify all of the priuses to use half the gas that they already did, based on which would have the greatest impact on gasoline usage.
Maybe I misunderstood the original intent.
Cindy

 

[GorD]

I'm with you on this one Cindy - you still have to use both types of car to fulfil the same milage rquirements.

According to the blog the answer is the 10 to 13 mpg change

(I still can't get my head around all this talk of suburbans, prius's gasoline and tires (with an I)

 

[Gerald Higgins]

Surely Cindy is right on this.
Assuming the number of cars, and their mileage, remains constant, then the option that reduces fuel consumption the most, is replacing the tyres.
True, altering the Prius does deliver a larger percentage reduction in consumption for the Prius, but that wasn't an objective in the puzzle as originally stated.

Of course these options ignore the cost of doing these things. How much do new tyres cost, as compared to re-wiring the Prius ?

 

[Scott Huish]

Yes, the Suburban has a greater reduction in gasoline that it uses but that's only because it used so much dang gasoline in the first place.

To round it off:

25% of 100 is more than 50% of 20.

The goal according to the question was to reduce gasoline usage. Since the Prius already did this better to begin with, improving it's gas mileage will reduce gasoline usage more than the gas hogging Suburban.

The Prius saved 80 gallons in the first place, and approxmately 67 gallons after the modification.

67 gallons is a lot of gas to use compared to 20. The Prius is still the best choice rewired or not to reduce gas consumption.

 

[GorD]

I don't think anybodys arguing which is the better car - but if you have 10 employees who all need a car and these are the 10 cars you have (5 of each and all the employees are going to do the same mileage) then changing the 10 mph to 13 will save you more Petrol.

Can't see it any other way

 

[RobMatthews]

I don't think anybodys arguing which is the better car - but if you have 10 employees who all need a car and these are the 10 cars you have (5 of each and all the employees are going to do the same mileage) then changing the 10 mph to 13 will save you more Petrol.

Can't see it any other way

Agree.

If you look at your first table, HotPepper,
Option A (per the question) will use 96.92 gallons. (76.92+20) (Improved 'burban)
Option B uses 110 gallons. (100+10)

(original uses 120 gallons).

Can't get much clearer than that?

 

[Scott Huish]

OK, I see where I went wrong now. Thanks. It's one or the other but you will still have both vehicles. You can't go with all Priuses, which of course would be the better solution.

 

[pgc01]

Since we all love Excel on here I thought I would put a brain teaser on that involves grids (you will probably end up drawing it in Excel anyway ha ha)

You have a 5 by 5 grid

You have to fit 5 Dogs and 3 cats into this grid

Imagine that the Dogs can move like a queen on a chess board,

Heres the puzzle, you have to position all 8 (5 Dogs and 3 Cats) onto the 5 by 5 grid so that all of the Cats are safe.

No tricks or anything like that, just pure logic! and it can be done many diff ways but is remarkably difficult.

Hi

Nice puzzle.

I checked the possible solutions and there is fact just one solution, in the sense that all the other ones can be obtained with operations like rotation or simmetry.

I then checked 4 cats and 4 dogs and there is more that one solution. I found one of the solutions very interesting, military like.

 

[Andrew Fergus]

I then checked 4 cats and 4 dogs and there is more that one solution. I found one of the solutions very interesting, military like.

Would that involve each dog occupying a corner square?

 

[pgc01]

Would that involve each dog occupying a corner square?

Hi Andrew

Yes, it's like the cat's are back to back, protecting each other and covering all directions. The dogs are atacking from 4 directions at 90 degrees.

On the other hand it could be the dogs playing poker at the center and the cats watching from a respectful distance.

This may be a good idea for one of my next problems. With some flexibility like variable number of cats, dogs and board dimensions.