determine formula for percentage

[Shannon]

I am adding B11 through B37, the subtotal appears in B39. In B40 I want to
display 15% of B39. Then in B41, B40 will be added for a grand total. These
figures are $amounts. I need to know the formula I would use in B39

 

[Luke M]

formula in B39:
=SUM(B11:B37)
in B40:
=B39*15%
In B41:
=B40+B39

Cell B40 may initially spit out a number with multiple integers, simply
format to collar. If you need to avoid the possibility of lost decimals,
formula in B40 could be changed to:
=ROUND(B39*15%,2)

 

[cm]

b39: =sum(b11:b37)
b40: =b39*0.15
b41: =b40+b39