Math - Decimals Subtraction

Slick subtraction in 3-D space has great tutorials, frustrating games

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Subjects & Skills

Character & SEL, Critical Thinking, Math

Price: Free, Free to try
Platforms: Android, iPad, Kindle Fire

Pros: Slick, 3-D graphics, fantastic tutorials on the standard decimal subtraction algorithm in three different situations.

Cons: Games are repetitive, tutorials aren't well-integrated into play, and the gender bias is blatant.

Bottom Line: This slick 3-D math app has unique tutorials and cool space theme, but games don't live up to graphics.

Kids could play around with the app as a warm-up or for fun, and the video tutorials, hosted by some pretty cool 3D dudes, might be worth showing as an introduction to decimals subtraction.

Math – Decimals Subtraction is an app that teaches kids a handful of decimal subraction techniques. Fifth- and sixth-graders can learn how to subtract decimals in three categories: subtracting whole numbers from decimals, subtracting decimals from whole numbers (trickiest), and subtracting decimals from decimals. Kids can learn to work quickly to beat timers, and to assess their own work through performance pages at the end of games and pre-post tests. 3-D figures talk kids through the steps in the tutorial section with examples in large numbers.

Kids create a username, select a "friend" avatar, and wander around their virtual room where they tap a TV to enter the games. New users take a 10-item pre-test to "get you warmed up for interesting games ahead." In the Intergalactic Baseball Championship game, kids are supposed to select a correct answer in about 18 seconds, which shortens to 10 when "trick ball" is displayed. Hungry Monster requires kids to select a correct answer and then tap on the advancing alien to distract it with a handful of fish. Super Store requires kids to mentally subtract cost from "amount paid," which is entered into a "balance" display. Kids earn bronze, silver, or gold stars at the end of each game, and a performance table lists all the data: expressions, correct answer, and answer given plus totals. User profiles save test data, but performance data is not saved from one game to the next.

It's graphically slick with good tutorials that give kids a solid background in decimal subtraction, but its games aren't that engaging. The developers made an effort to create a pedagogically sound educational game, but in the end, the results are disappointing. Functionality feels disjointed, and text is often hard to read. Tutorials -- the app's best feature -- aren't integrated into play, so kids may overlook them. Plus, they don't address the mental math strategies kids need to do the game's multi-digit calculations. If the games had a built-in calculator that kids could access while playing instead of focusing purely on mental math, the experience might be less grueling. Tests are tedious, have confusing instructions, and include skills the games don't address. Feedback on the baseball mini-game is unintuitive, with correct answers resulting in a strike and incorrect answers earning a home run.

But wait, there's more! The female avatar has her hands on classically cocked hips tossing her head back suggestively. And stragely, she and her male counterpart have no role within games, which feature some other boy pitching a baseball at an alien or saving a girl from an alien by lowering a ladder -- a girl who happens to be hunched over and completely inactive. With all the options available, different choices could have been made.

Learning Rating

Overall Rating

High-production-value graphics in 3D are visually appealing, and kids will really enjoy customizing their space-themed room within the game. However, the games themselves could be more cohesive and have easier to read text.


The audiovisual tutorials do a great job of describing the basic algorithm for subtracting decimals, but kids need more advice on mental math skills to perform well in games. Also, female characters are represented as weak or sexy. 


Performance page provides great detail on how well kids scored on each game, but some kids may have difficulty with the hard-to-read text and unintuitive game interface. 

Common Sense reviewer

Community Rating

If your students struggle with subtracting decimals then this app might be the one for them. Using games, tutorials and the ability to earn trophies students have the opportunity to mastersubtracting decimals.

As a teaching tool this could be very helpful for students that struggle with decimal subtraction. I was not impressed with the customizing features that students could select (changing outfits, etc) as I want students to focus in on the mathematical skills that need to be mastered. My students all became very aware of the fact that it was okay to use paper and pencil and that many operations in math cannot be done mentally. There are just so many ways that you can teach this math concept so engaging students with the game structure did help them to stay on task and not turn them off by using worksheets.

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