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Here is a comprehensive list of math apps thanks to the University of Michigan:

Compatible with iPhone, iPad, and iPod touch. Requires iOS 7.0 or later. This app is optimized for iPhone 5.
This app’s draganddrop technology helps make algebra easier by allowing you to shuffle the terms between sides of the equations.

Compatible with iPhone, iPod touch, and iPad. Requires iOS 3.0 or later.
Learn basic addition and subtraction in a fun easy way with this app. You can change the difficulty level as you progress.

Compatible with iPhone, iPod touch, and iPad. Requires iOS 4.3 or later.
Learn how to recognize, count, add, and make change with U.S. coins.

Compatible with iPhone, iPod touch, and iPad. Requires iOS 6.0 or later. This app is optimized for iPhone 5.
This powerful free app has many robust features, including graphing multiple equations at once, labeling graphs, converting units of measurement, and more.

Compatible with iPad. Requires iOS 6.0 or later.
Developed by CAST, MathScaled contains several balancescale based math puzzles. Users have to place different shapes on the scales to balance them out, without knowing the weights of the shapes. The app can also track your progress.

Compatible with iPad. Requires iOS 6.0 or later.
Developed by CAST, MathSquared contains several gridbased math puzzles of varying difficulty to help teach basic math operations. Users can develop their logical thinking and reasoning skills and receive progress reports along the way.

Compatible with iPhone, iPod touch, and iPad. Requires iOS 4.3 or later. This app is optimized for iPhone 5.
This app provides visual math fundamentals for kids learning math with a learning disorder. The app benefits every child in helping them to grasp the fundamentals of math.

Compatible with iPhone, iPad, and iPod touch. Requires iOS 5.0 or later. This app is optimized for iPhone 5.
This multiperson app allows up to 50 students to practice simple mathematical functions. Each student’s questions are customized to his/her strengths and weaknesses, and progress reports are available.

Compatible with iPhone, iPod touch, and iPad. Requires iOS 4.3 or later.
This app can help you master simple mathematical functions — addition, subtraction, multiplication, and division. It can also be customized to focus on a particular fact, such as multiplication by 1 or 0.

Compatible with iPhone, iPod touch, and iPad. Requires iOS 5.0 or later. This app is optimized for iPhone 5.
Park Math provides kids with a fun way to learn math. Learn to count, add, subtract, sort, and more, all while playing at the virtual park.

Compatible with iPhone, iPod touch, and iPad. Requires iOS 5.1 or later. This app is optimized for iPhone 5.
Quick Graph is a powerful scientific graphing calculator app. It features unlimited graphs, VGA output, 2D and 3D equation plotting, and much more.

Compatible with iPhone, iPod touch, and iPad. Requires iOS 5.0 or later.
Rainbow Math is the perfect app for elementary children to learn the four basic functions of math—addition, subtraction, multiplication, and division. The app is designed with fun images and colors to keep kids interested.

Compatible with web browsers on desktops, laptops, and iPad.
Shape Math uses pictures and shapes to help you do simple mathematic equations, calculate tips at a restaurant, or do mental math.

Compatible with iPad. Requires iOS 6.0 or later.
These apps are gradespecific, making it easy for students to practice math skills for grades 15. All content is aligned to the common core standards.

Compatible with iPhone, iPod touch, and iPad. Requires iOS 4.3 or later. This app is optimized for iPhone 5.
Talking Scientific Calculator can read numbers, answers, and formulas aloud to you. It has two entry modes, and the entire app is accessible to VoiceOver users.

Compatible with iPad. Requires iOS 4.3 or later.
This app helps you learn multiplication visually by displaying graphically rich multiplication tables.