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## Unit of measure problems  2-Guest

## Unit of measure problems

MathCAD is changing or not recognizing the unit of measure. The answer would be 28000 MPa

1 ACCEPTED SOLUTION

Accepted Solutions  24-Ruby V
(To:luizhcastanho)

As Luc already explained, Prime is perfectly right. If you take the root of fck you also take the root of its unit.

It looks like you are using an empirical formula. That kind of formula was used with pocket calculators (or even slide rulers) which can not deal with units. Usually you were told that you have to input this variable in unit km and that variable in unit Mpa and if you do so you get the result in kV. They meant to input just the appropriate numbers of course.

To deal with that kind of formulas which often don't balance units you have to do what they demand - input just the numbers, considering the unit the formula expected and add the unit they tell you the result would be in yourself.

To do this in Prime you divide the variables by the demanded units and add the correct unit to the result.

In your case fck is obviously expected in MPa and the result should be in MPa, too. So you would do it that way: 2 REPLIES 2  23-Emerald III
(To:luizhcastanho)

No, Prime is right.

You're taking the square root of a value in Pa, then the result has units sqrt(Pa).

Success!

Luc  24-Ruby V
(To:luizhcastanho)

As Luc already explained, Prime is perfectly right. If you take the root of fck you also take the root of its unit.

It looks like you are using an empirical formula. That kind of formula was used with pocket calculators (or even slide rulers) which can not deal with units. Usually you were told that you have to input this variable in unit km and that variable in unit Mpa and if you do so you get the result in kV. They meant to input just the appropriate numbers of course.

To deal with that kind of formulas which often don't balance units you have to do what they demand - input just the numbers, considering the unit the formula expected and add the unit they tell you the result would be in yourself.

To do this in Prime you divide the variables by the demanded units and add the correct unit to the result.

In your case fck is obviously expected in MPa and the result should be in MPa, too. So you would do it that way:  Announcements