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.

CE Marking to EU Directives

When designing the machine for the customers in Europe, I have to make sure that the machine has full CE compliance.

By the way, what is CE?

I search for more details about CE and put them here for more understanding.

The CE marking is an acronym for the French "Conformité Européenne". By affixing the CE marking, the manufacturer, or in certain cases another legal person responsible for the product, asserts that the item meets all the essential "Health and Safety" requirements of the relevant European Directive(s) that provide for the CE marking. Examples of European Directives requiring CE marking include toy safety, machinery, low-voltage equipment, medical devices and electromagnetic compatibility.

CE Marking Procedure

The "New Approach" to conformity enables manufacturers to use what is called as "SELF DECLARATION" where the manufacturer himself declares conformity by signing the "Declaration of Conformity (DOC)" and then affixes the CE Mark on his product.

The following simple steps are involved
STEP 1: Identify Applicable "DIRECTIVES"
STEP2 : Identify Applicable "Conformity Assessment Module"
Although CE Marking follows the Self Declaration principle, depending upon product complexity and risk to human life, various conformity assesment module are prescribed:-
Module 'A' (Internal Production control).
Applicable for products falling under EMC and Low Voltage Directives. Manufacturer tests the product from third party. After compliance with the tests, his production process ensures continued conformance. He maintains "Technical Documentation" as a proof of compliance. There is No mandatory involvement of European Lab (i.e. Notified Body).
Module 'B' to 'H'
Mandatory involvement of European Lab is required which issues "Type Examination Certificate", certifies documentation (called "Techncal Construction File"(TCF) and carries out inspections.
STEP3 : Identify Applicable "Standard"
STEP4 : Test one sample of the productEither yourself or from test lab.
STEP5 : Compile "Technical Documentation"
STEP 6 : Sign the EC "Declaration of Conformity"
STEP 7 : Affix "CE Mark" on the product.


There are 21 European "New Approach" Directives against which a wide range of products are required to be CE marked against before they are "placed on the market" in Europe. When placing the CE mark on the product the manufacturer or "his authorized representative in the European union" is declaring that the product complies with all applicable directives. The list of 21 applicable directives can be found on the European Commission website. The EU Directives are not themselves law as they are all taken into the the law of each member state. Whilst the directive and standards may be harmonized across Europe manufacturers still need to be aware of country specific requirements in safety standards, permitted frequency bands and other areas that might affect their product.

Some directives requirements are more onerous than others, but a general guide is that a manufacturer must

  • identify all directives applicable to their product
  • assess their product against the requirements of a directive - usually through a combination of technical argument and testing. Testing can be done in house by the manufacturer or by 3rd party specialist test laboratories
  • create a Technical File containing full details of the product and all assessments carried out to demonstrate compliance. This technical file becomes a living document and needs to be kept up-to-date as changes occur to the product or to the standards against which the product was assessed
  • depending on the directive there is an optional or mandatory requirement to have the Technical File assessed by a Notified Body
  • Draw up and sign a Declaration of Conformity and affix CE mark to the product and/or packaging

Charlie is a CE marking consultant at DheaniSulis Ltd who specialise in helping companies navigate their way through these product approval requirements in a timely and cost efficient manner.

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