# Number Thumber: Mental Math — The mental arithmetic workout > Interactive game for practicing mental arithmetic by filling in missing digits. (iPhone/iPad app by Baibysoft Ltd.) - Source: https://appshunter.io/ios/app/number-thumber-mental-math/id6756803242 (this page in markdown: same URL + `.md`) - Developer: [Baibysoft Ltd](https://appshunter.io/developer/1862950062) - Category: Education, Games, Casual, Puzzle - Price: Free with in-app purchases - Rating: 5.00/5 from 1 App Store ratings - Age rating: 4+ - Requires: iOS 13.0 · 111 MB - Languages: English - Released: 2026-01-05 - Data updated: 2026-06-18 - Monetization: free with in-app purchases - User reviews in markdown: https://appshunter.io/ios/app/number-thumber-mental-math/id6756803242/reviews.md ## What is Number Thumber? The goal of the game is to provide the missing digits in the arithmetic expressions. There are always at most two missing digits, and one is always to the right from another. The digits are filled by tapping on or sliding over the two controls containing digits from 0 to 9 at the left and right edges of the screen or game window. Left control drives the left missing digit and right control drives the right one. If only one digit is missing in the expression, then it can be chosen by either of the controls. On the mobile devices with the touch screens, the digit controls are most easily operated by the thumbs, hence the name of the game. If the keyboard is present, then the regular numeric keys control the left digit and the keypad keys, if the keypad is present, control the right digit. Both sets of the numeric keys control a single missing digit. Mouse can also be used to click on both the left and the right number controls on the screen. Each problem is given a limited time to be solved, as indicated by the progress bar at the bottom. The correct solution is auto-recognized one second after the numbers were last chosen. If the solution is provided, then the expression will “blow up”. To force immediate acceptance and not wait for a second, tap on the problem area. If the expression won’t blow up this means that your solution is wrong. If the correct solution is not provided during the allocated time, the correct solution will be shown for 3 seconds. Tap on the problem area to force generation the new problem without waiting for 3 seconds. To force regeneration of the problem, tap on the “fast forward” control, to the right of the “play/pause” button Each problem type has its score depending on the complexity. If the keyboard is present, then one can force immediate acceptance or skip viewing the correct answer by pressing “spacebar”. To fast forward to the next problem, press Escape of Tab key. The total score is displayed in the top middle of the screen. The number of seconds allocated for solving a problem is 5 plus the problem’s score. SETTINGS The Settings screen always choosing the types of problems and configuring them. There are to two settings, applied to all problems. a. Calculation vs missing number problems, i.e. A+B=_ vs A+_=C. b. Fractions of the negative terms, the extreme examples would be A-B vs -A-(-B), where A and B are always positive. Problems of five types are available. A problem type is added to the game by checking the checkbox next to it. 1. Simple single step addition, subtraction, multiplication or division. You can choose which of the four operations are included. In the case if additional, each term will be less than 100, and if negative terms are not allowed, then the difference of a subtraction will always be positive. Multiplication and division terms go up to 12. 2. Long operations: addition, subtraction and multiplication. All terms and the result are guaranteed to be positive. The largest term is always more than 100, and the second multiplication term is one digit. 3. Nested brackets: expression like A+(B-(C-D)). It is possible to choose the number of nesting, between 1 and 4. The terms are always one-digit. 4. Multistep expressions: up to two multiplication or divisions, connected by an addition or a subtraction, e.g. AxB – C/D, or A + CxD. 5. Fractions: addition, subtraction, multiplication and division of proper fractions. You can save, edit and delete your game configurations, using the controls on the left half of the Settings screen. Two configurations are provided by default and cannot be edited or deleted. Simple configuration only has the one step problems, containing all operations. Full configuration has all problems, with default settings for the fraction of the missing number problems (33%) and negative terms (25%). https://www.apple.com/legal/internet-services/itunes/dev/stdeula/ ## Key features - Fill in missing digits in arithmetic expressions - Timed challenges with progress bar - Customizable problem types and operations - Support for addition, subtraction, multiplication, and division - Adjustable difficulty with fractions and negative terms - Score-based time allocation ## Pricing and in-app purchases Base price: Free. **Subscriptions** | Subscription | Price | Period | | --- | --- | --- | | Number Thumber monthly | $1.99 | per month | **One-time purchases** | Purchase | Price | Type | | --- | --- | --- | | NT School Trial 1m | $0.99 | one-time | ## Frequently asked questions about Number Thumber ### How does Number Thumber work? Number Thumber presents arithmetic expressions with missing digits. Players tap or slide controls to input the correct numbers within a time limit to solve the problems. ### What types of math problems are available in Number Thumber? The game supports single-step addition, subtraction, multiplication, and division. It also includes options for fractions and negative terms, allowing for more complex calculations. ### Can I customize the difficulty of Number Thumber? Yes, you can customize the types of problems, including which operations are included. You can also configure settings for fractions and negative terms to adjust the challenge. ### How is progress tracked in Number Thumber? Each problem is timed, and a progress bar indicates the remaining time. Correct solutions are auto-recognized, and a score is displayed, with the time allocated for solving problems increasing with the score. ### What devices is Number Thumber compatible with? Number Thumber is available on Mac, iPhone, iPad, and iPod, making it accessible across various Apple devices. ### Does Number Thumber have ads? No, Number Thumber does not contain advertisements, providing an uninterrupted learning experience. ### What is the subscription model for Number Thumber? Number Thumber offers a monthly subscription plan for $0.99, providing access to premium features or content. ### How often is Number Thumber updated? The latest version of Number Thumber is 2.06.00, and it was last updated on April 28, 2026, indicating regular maintenance and potential feature additions. ## Version history (last 4 releases) ### 2.06.00 — 2026-04-28 Added support for the trial versions. ### 2.00.04 — 2026-03-02 Fixed a bug in the payment flow ### 2.00.02 — 2026-02-11 New app icons ### 2.00.01 — 2026-01-05 No release notes. ## Apps similar to Number Thumber | App | Rating | Price | Category | | --- | --- | --- | --- | | [Kaligo](https://appshunter.io/ios/app/kaligo/id1345325412) | — | Free | Education | | [3rd grade learning game](https://appshunter.io/ios/app/3rd-grade-learning-game/id1567588856) | 4.6 (109) | Free | Education | | [Army Cognitive Test 2026](https://appshunter.io/ios/app/army-cognitive-test-2026/id1611115652) | 4.8 (9) | Free | Education | | [MyOxford University](https://appshunter.io/ios/app/myoxford-university/id6636474788) | — | Free | Education | | [FunLab: Science Games for Kids](https://appshunter.io/ios/app/funlab-science-games-for-kids/id6670397096) | 4.7 (310) | Free | Education | | [CFAB Practice Exams](https://appshunter.io/ios/app/cfab-practice-exams/id1522171791) | — | $9.99 | Education | --- *Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-06-18.*