The Office Discipline Referra application's logo which is a wooden board with the letters O.D.R routed into it.

Terrific Triangle

Build creative equations while practicing math facts


A math facts  drill-and-practice program that teaches fact families for both addition/subtraction and multiplication/division.
What it does:   The triangle presents two parts of a fact family and the player must determine the missing third part. The sum and product always appear at the top of the triangle. The addends and factors always go in the two lower corners.
Free:   There are no in-app purchases or advertisment banners.

Screen Shots

A thumbnail of a portrait Android phone displaying an addition / subtraction problem against a timer in the Terrific Triangle app. A thumbnail of a landscape Android phone showing a multiplication / division problem against the timer in the Terrific Triangle app.
A thumbnail of a portrait Android phone showing the preferences screen for the Terrific Triangle app. A thumbnail of a landscape iPad displaying an addition / subtraction screen (with timer)from the Terrific Triangle app.


App store badge with an apple and reflective gloss.
Google Play store badge.

System Requirements

iOS 10.x or later
For iPhone, iPod touch, and iPad
Android 7.0 (Nougat) or later
MacOS 10.9 (Mavericks) or later
Windows 7 or later


  • version 1.4  February 2024 (mobile) / April 2024 (desktop)         Changed the difficulty preferences to allow more granular control. Added a detailed description of the exact problems associated with each difficulty level. Bug fixes.

  • version 1.3.5  August/October/November 2023  (Android, Macintosh and iOS versions only) - Modernized the API usage to maintain compatability with Google Play store. Minimum Android OS was increased from 5.1 (Lollipop) to 7.0 (Nougat). The Macintosh version is now compiled to run natively on both Intel and Apple processors. Improved compatibility with MacOS 14 (Sonoma). Improved compatability with iOS 17

  • version 1.3.4  February 2022 - Improved the ability to draw and position the lemniscate animation. Added a simple "Help" sheet to MacOS & Windows. Fixed the toggle switch's poor behavior on Windows.

  • version 1.3.3  February 2022 - (iOS only) Lowered the minimum iOS version. (Will work on the iPhone 5 again!) Added two animations as additional rewards for correct answers. Minor cosmetic improvements.

  • version 1.3.2  August 2020 - Improved keypad entry and provided better feedback for correct answers. [iOS version requires iOS 12 or higher.]

  • version 1.3.0  August 2019 - Added support for Android. Mac version is now 64-bit. Both Mac and Windows versions are now code signed.

  • Originally written for MacOS in 2003 by Scott Morrow for use in his third grade classroom as a supplement to the Everyday Mathematics program (SRA / McGraw-Hill.) Rewritten in 2018 for use on iPads in his second grade classroom.

  • Written with Livecode   green LiveCode programming language icon
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