calculating the area of a circle with bc

[Rei Shinozuka]

The area is proportional to the square of the diameter or radius.

Data form www.dominos.com:

Domino's 10" pizza is $7.00
Domino's 14" pizza is $11.99.

The 10" price/diameter is 70 "cents per inch."
The 14" price/diameter is 85 "cents per inch."

implying that the 10" is a better buy.

But price/area shows:

The 10" price/area is 8.6 cents per square inch.
The 14" price/area is 7.7 cents per square inch.

The 14" pizza is 10% cheaper than the 10" pizza.

For a pure comparisons, you are correct: coefficients like pi are not 
needed to compare.  But you need to square the linear size of the pizza.

-rei


On 03/28/2010 03:24 PM, Tony Arnold wrote:
> Jozsef,
>
> Since the area of a pizza is directly proportional to its diameter, you
> only really need to calculate the price/diameter to find out the best
> value for money!
>
> Regards,
> Tony.
>
> Jozsef Vadkan wrote:
>    
>> input like:
>>
>> sh count.sh 0.45 2200
>> ...
>>
>> explanations:
>> 0.45 =>  diameter [in meter]
>>
>> 2200 =>  e.g. xy money
>>
>> $(echo "scale=100; 2^($1/2) * $(echo "scale=100; 4*a(1)" | bc -l)" | bc
>> -l) =>  area of the circle
>>
>> xy money =>  some nations currency
>>
>>
>> i'm dividing the area of the circle because i want to get the "xy
>> money/square meter"
>>
>>
>> #!/bin/bash
>>
>> echo "$2/$(echo "scale=100; 2^($1/2) * $(echo "scale=100; 4*a(1)" | bc
>> -l)" | bc -l)" | bc -l
>>
>>
>> is there a shorter/better way?
>>
>>
>> it would be a pizza price calculator. [:D]
>>
>> 45 cm pizza = 2200 xy money
>> 30 cm pizza = 1260 xy money
>> 22 cm pizza = 960 xy money
>>
>> i just want to count that, what will i have to choose to get the best
>> price for "xy money/square meter" pizza.
>>
>> don't laugh. [:D]
>>
>>
>>      
>