How To Calculate Basic Salary From CTC

Hi Friends
I want to know how to calculate the Basic Salary from CTC.
Some of my friends has told me that "this is the reverse calculation of the salary"
I am confused plz help me
My company has Basic salary as 55%, HRA 40%, CCA Rs. 800/-, Medical 1250/-, & Spl Allowance the total of the above calculation is Gross Salary
Company will pay apart from the salary is as follows
1. Employer Contribution towards the pf is Rs. 780/-
2. Group Medical Insurance Rs. 1000/- (appx)
3. Meals Coupan Rs. 1250/-
Please send me the reply with example at the earliest.
Thanks & Regards
Ravi

if annual CTC is given how we will distribute it to BASIC where 50% of the basic is given as HRA and the amount that is calculated as basic is also given as annual bonus
My query is if an employee Annual CTC is 200000 how much would he be paid as basic medical and education

Basic
HOUSE RENT ALLOWANCE
MEDICAL REIMBURSEMENT
EDUCATION ALLOWANCE
CONVEYANCE ALLOWANCE
LEAVE TRAVEL ASSISTANCE
PF ( EMPLOYER CONTRIBUTION)
OTHER ALLOWANCE

Hi
My understanding of CTC is as under:-
The CTC is divided into two/three parts i.e. Base Pay, Choice Pay and in some companies PLI.
Let us assume:-
CTC 100
Base Pay 40
Choice Pay 50
PLI 10.
Now, the Base Pay includes Basic Pay, PF Contribution of Employer and Gratuity
PF Contribution 12% of Basic Pay and Gratuity is 4.81% of Basic Pay.
So the formula for calculation of Basic Pay would be
Basic Pay = Base Pay/ 1.681
Choice Pay can be the amount which an employee have the option to decide from the given options.
and, the PLI is Performance Linked Incentive which is payable at the end for the period, based on individual's performance.
Thanks
Pawan