Improve math skills of your kids - Learn step-by-step arithmetic from Math games

Math: Unknown - Step-by-step math calculation game for iOS.

Math: Unknown is much more than a math game. It is a step-by-step math calculation game which will teach users how to calculate in the correct order rather than just asking only the final calculated results.

The app consists of four basic arithmetic operations which are addition, subtraction, multiplication and division. In order to get started, users who are new to arithmetic can learn from animated calculation guides showing step-by-step procedures of solving each type of operation. It is also helpful for experienced users as a quick reference.

Generally, addition and subtraction may be difficult for users who just start learning math especially when questions require carrying or borrowing (also called regrouping). The app helps users to visualize the process of carrying and borrowing in the way it will be done on paper. Once users understand how these operations work, they are ready to learn multiplication and division.

For most students, division is considered as the most difficult arithmetic operation to solve. It is a common area of struggle since it requires prior knowledge of both multiplication and subtraction. To help users understand division, the app uses long division to teach all calculation procedures. Relevant multiplication table will be shown beside the question. Users will have to pick a number from the table which go into the dividend. Multiplication of selected number and divisor is automatically calculated, but the users have to do subtraction and drop down the next digit themselves. Learning whole calculation processes will make them master it in no time.

Math: Unknown is a helpful app for students who seriously want to improve arithmetic calculation skills.

Engineering Plastic POM Polyacetal

Normally, we use steels to make machine components. But in some applications, engineering plastics are also commonly used in machine parts since their unique properties e.g. lighter weight, easy for machining, great quantities can be made quickly by injection, etc.

General properties of engineering plastics:
Light weight - The density of engineering plastics is usually about 1-2 g/cm3. We often use them in the portable machines that we often move them, or use in the parts that the user has to hold by hand.

No rust - We normally use engineering plastics without surface treatment to prevent rust. However, engineering plastics do not withstand the corrosion from oxygen or ultraviolet, so we need to consider this point when using plastic for long time.

Low electrical conductivity - We use plastics to prevent users from direct contact with electrical parts for safety reason.

Low thermal conductivity - Engineering plastics are good for insulation. We can prevent some heat from machine. However, they usually cannot withstand high temperature and they may deform and strength reduced.

POM or Polyoxymethylene , also known as acetal, polyacetal and polyformaldehyde is an engineering thermoplastic used in precision parts that require high stiffness, low friction and excellent dimensional stability. We use POM to make gears, cams, bearings, guides, rollers, etc. It normally has milky color or black color. Its tensile strength is about 60 MPa which is 1/7 of the strength of SS400 steel and the weight is about 1/7 of steel. It can be used for sliding application. Working temperature should be within - 40oC to 105oC.