Question type - Equation
From LimeSurvey Manual
Short description
This question type lets the author create an equation (e.g. a calculation or tailored report) and save it in a database variable. Equations can use any syntax supported by Expression Manager. If you are handling numeric values make sure that you use the advanced question setting 'Numbers only' as explained below.
Core settings
{INCLUDE(page="Core question settings",start="!mandatory",stop="---")}{INCLUDE}
{INCLUDE(page="Core question settings",start="!relevance",stop="---")}{INCLUDE}
Advanced settings
{INCLUDE(page="Advanced question settings",start="!hidden",stop="---")}{INCLUDE}
Note: unlike all other question types, if an equation is hidden, it is still computed and its value is still stored in the database.
{INCLUDE(page="Advanced question settings",start="!numbers_only",stop="---")}{INCLUDE}
{INCLUDE(page="Advanced question settings",start="!page_break",stop="---")}{INCLUDE}
{INCLUDE(page="Advanced question settings",start="!public_statistics",stop="---")}{INCLUDE}
{INCLUDE(page="Advanced question settings",start="!scale_export",stop="---")}{INCLUDE}