Mathematical Operator in an expression

Question

I am using the expression below to calculate the distance, however the parser is unable to process this expression

 

Distance = (1/2) * (GRAVITATIONAL_FORCE) * (time *2)

 

 

If i use the above expression as below it works.

 

Distance = FRACTION * GRAVITATIONAL_FORCE * (time * 2)

• FRACTION = 0.5  

 

 I have tried to assign FRACTION = (1/2), and use FRACTION as variable in above expression it does not work either. 

 

Please suggest what is wrong with the first expression. 

 

 

Also, is there a function for a square of a number? in above expression  time is a variable that need to be square, I have been writing expression as (time *time) or (time * 2)