Marginal Costing
·        
Total cost + Profit  = Sales    
·        
Total Cost = Variable
Cost   +  Fixed Cost  
·        
So, Variable Cost
+ Fixed Cost + Profit  = Sales
·        
Sales = Variable Cost + (Fixed
Cost + Profit) 
·        
Contribution = (Fixed Cost + Profit)
·        
Sales - Variable Cost = Contribution
·        
I.e., S - V = (F + P) 
or 
·        
S - V = C
or
·        
C = S - V 
·        
Contribution = Sales - Variable Cost
·        
Contribution = (Fixed Cost + Profit)
·        
(Fixed Cost + Profit) = Sales - Variable Cost
·        
Profit Volume Ratio (PV Ratio) = Contribution
/ Sales
·        
BEP - Break Even Point = Where No Profit or No
loss.
·        
BEP - Break Even
Point = Fixed Cost / P V Ratio
Problem:
Sales - Rs. 100, 
Variable Cost - Rs. 80,  Fixed
cost - Rs. 10.   Find the Sales at Break
Even Point
Answer:
Contribution = Sales - Variable Cost
C = Rs. 100 - Rs. 80 = Rs. 20
PV Ratio = Contribution / Sales = Rs. 20/ Rs.100  = 0.20
BEP = Fixed Cost / PV Ratio
BEP Sales = Rs.10 /0.20 
= Rs. 50
To Prove: 
If Sales is Rs. 100, 
Variable Cost is Rs. 80
If Sales is Rs. 50, Variable Cost is ?   = 50/100 x 80  = Rs. 40
Contribution = Sales -
Variable Cost   Rs. 50 - Rs. 40
= Rs. 10
In Break Even Point, Contribution equals Fixed Cost.  Here too Contribution (Rs. 10) and Fixed Cost
(Rs.10) are equal. That means No Profit or No loss at Sales Rs. 50.
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