# Calculating Energy Costs - mathjs with variables

**URL:** <https://community.homey.app/t/calculating-energy-costs-mathjs-with-variables/46881>\
**Category:** Questions & Help\
**Created:** [April 30, 2021, 5:51am UTC](https://community.homey.app/t/calculating-energy-costs-mathjs-with-variables/46881 "2021-04-30T05:51:51Z")\
**Posts on this page:** 1\
**Showing post:** 6

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**Author:** ![Rocodamelshekima](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/rocodamelshekima/32/8209_2.png) [@Rocodamelshekima](https://community.homey.app/u/Rocodamelshekima)\
**Post date:** [April 30, 2021, 5:45pm UTC](https://community.homey.app/t/calculating-energy-costs-mathjs-with-variables/46881/6 "2021-04-30T17:45:30Z")

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So reading [this post](https://community.homey.app/t/get-a-notification-when-the-washingmachine-is-ready/9372/6) only gives u boolean variables?  
And sending a txt message with a Better Logic variable don’t work for u?  
One of the lines is: “Make an extra variable and make it a number variable. In my case i called it “KwHtarief”.”  
Where do u see boolean variables?

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