calculating the area of a circle with bc

[Tony Arnold]

Rei,

Rei Shinozuka wrote:
> 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.

I stand corrected again. And I thought I was good at maths!

Regards,
Tony.

> 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]
>>>
>>>
>>>      
>>    
> 
> 

-- 
Tony Arnold,                        Tel: +44 (0) 161 275 6093
Head of IT Security,                Fax: +44 (0) 870 136 1004
University of Manchester,           Mob: +44 (0) 773 330 0039
Manchester M13 9PL.                 Email: tony.arnold at manchester.ac.uk