[Tutor] Is this correct?

[bob gailer]

Please always reply-all so a copy goes to the list. We all participate 
and learn.

Would you also respond to my requests for clarified algorithm?

cclpianos at comcast.net wrote:
> Hi Bob, 
>
> Thanks for your input! I ran the program in IDLE and it worked just 
> fine. Apparently my calculations were correct, although sloppy. Some 
> very good points for me to consider;

Thanks for the acknowledgment.
>
> Indentation. I felt for myself it was a bit more readable, but 
> considering I'm new and the formatting may not survive other OS's, I 
> plan on making those changes.

> The use of the 1.041 for the interest rate. Here, as I'm not 
> mathematically inclined I don't see the advantages, but I'll compare 
> the program to yours to see how it works.

Your calculation was, in effect, principal = principal + principal * 
interest. Do you recall factoring in algebra?

principal = principal * (1 + interest). For me it is a little easier on 
the eyes and thinking to see the latter.

You could also do:

principal += principal * interest



> Starting the count at 2 and eliminating the other if statements is a 
> great simplification.
> It all seems a bit clearer in your rendition. 
>
> Thanks again, 
> Pat
>
> On Feb 8, 2009, at 3:11 PM, bob gailer wrote:
>
>> principal = balance = 500000 # Starting fund amount.
>> interestRate = .05 # Interest rate added to the principal annually.
>> tuition = 34986 # Starting tuition fee
>> tuitionInc = 1.041 # The annual increase applied to the tuition.
>> print principal, "Is the starting principal" # This is to show the 
>> starting balance.
>> print tuition, "Is the starting tuition."
>> balance = principal - tuition
>> print balance," the amount remaining after first tuition deduction.  "
>> interest = balance * interestRate # calculates the amount added to 
>> the fund
>> print interest, "  Interest added to fund for one year. "
>> newBalance = balance + interest
>> print newBalance, "is the new balance."
>> count = 2 # keeps me informed on the number of students benefitting 
>> from this grant.
>> while principal > tuition:
>>  tuition *= tuitionInc # calculates the rising cost of tuition.
>>  if newBalance < tuition:
>>    print newBalance + interest
>>    newBalance = principal
>>    print principal," is the new balance. "
>>    interest = principal * interestRate
>>    print interest," is the new interest on the principal. "
>>    balance = principal + interest
>>    print balance,"is the new principal. "
>>  tuition *= tuitionInc # calculates the rising cost of tuition.
>>  print tuition," is the new cost of tuition. "
>>  principal = newBalance - tuition
>>  print principal," is the new balance. "
>>  interest = principal * interestRate
>>  print interest," is the new interest on the principal. "
>>  balance = principal + interest
>>  print balance, "is the new principal. "
>>  count = count + 1
>>  if tuition > principal:
>>    print principal + interest, "was available for the last student."
>> if count > 10:
>>  print count, "Students used this grant." 
>


-- 
Bob Gailer
Chapel Hill NC
919-636-4239