### 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.

### Chain Drives - Conveyor Roller Chain

Chain drives are an important part of a conveyor system. Chain drives are normally used to transmit power between a drive unit and a driven unit of the conveyor system. Chain drives can consist of one or multiple strand chains, depending on the load that the unit must transmit. The chains need to be the matched with the sprocket type, and they must be tight enough to prevent slippage.
" Chain is sized by the pitch or the center-to-center distance between the pins. This is done in 1/8" increments. "
Conveyor Roller Chain
Roller chains are made up of roller chain link that are joined with pin links. The roller chain links are made up of two side bars, two rollers, and two bushings. The roller reduces the friction between the chain and the sprocket, thereby increasing the life of the unit.

Roller chains can operate at faster speeds than plain chains, and properly maintained, they will offer years of reliable service. Some roller chains come with a double pitch, meaning that the pitch is double that of a standard chain, but the width and roller size remains the same. Double-pitch chain can be used on standard sprockets, but double-pitch sprockets are also available.
The main advantage to the double-pitch chain is that it is cheaper than the standard pitch chain. So, they are often used for applications that require slow speeds, as in for lifting pieces of equipment in a hot press application.
Roller chain is ordinarily hooked up using a master link (also known as a connecting link), which typically has one pin held by a C clip rather than friction fit, allowing it to be inserted or removed with simple tools. Half links (also known as offsets) are available and are used to increase the length of the chain by a single roller.

Roller chain is made in several sizes, the most common American National Standards Institute (ANSI0 standards being 40, 50, 60, and 80.
"The first digit(s) indicate the pitch of the chain in eighths of an inch, with the last digit being 0 for standard chain, 1 for lightweight chain, and 5 for bushed chain with no rollers."
Roller chain is used in low- to mid-speed drives at around 600 to 800 feet per minute; however, at higher speeds, around 2,000 to 3,000 feet per minute, V-belts are normally used due to wear and noise issues.

It is advisable either to monitor the exact length of a drive chain (the generally accepted rule of thumb is to replace a roller chain which has elongated 3% on an adjustable drive or 1.5% on a fixed-center drive), or just replace it at established intervals of use to minimize wear on the sprockets. Thus, any savings in maintenance costs from skimping on lubrication result in increased costs for monitoring wear and for replacement. This need for frequent maintenance, comprising lubrication, assessing wear, and replacement of the chain and/or the sprockets, represents the major drawback of the utilization of roller chain.

The lengthening of a chain is calculated by the following formula:

% = [M − (S * P)] / (S * P) * 100

M = the length of a number of links measured
S = the number of links measured
P = Pitch

Some contents from wikipedia.org