Units are not compatible

[Mike_Egan]

can someone please help.

i have tried everything but i can not get it to calculate.

Keeps saying Units are not compatible

[AlanStevens]

In M3 it looks like you are trying to add 1 (dimensionless) to r^2-b^2 (dimensions of length^2).

Similarly, in M4 you are trying to add dimensionless quantities to dimensional ones.

Alan

[ValeryOchkov]

What is the origin of the formulas?

May be it is an empirical formulas?

[Mike_Egan]

hi the formulas come from a pressure vessel design code, PD5500

[AlanStevens]

Compare your expressions with those in the design code very carefully.  You will see that you have got some of your division lines in the wrong place!

Alan

[Mike_Egan]

just noticed I have copied the formula down wrong, not I have sorted this it is still saying the units are not compatible, any suggestions ????

[Mike_Egan · Accepted solution]

done, all sorted, thank you all, it helps if I copy things down correctly, brackets and division in the correct place.