If you choose to add a percentage to the amount using their own mathematical abilities, start with the formulation of the forthcoming mathematical operations, as the correct formulation of the problem in any case is half of its solution. Assume that the percentage is one-hundredth share of the available amount. To Express the size of this one hundredth in monetary units need the entire sum to be divided into one hundred. For example, one percent of the amount of one hundred thousand rubles will amount to one thousand rubles. So, the original amount with the added percentage will be one hundred one thousand rubles. If such interest is necessary to add several (e.g. ten), then the amount of one percent (thousand rubles) it is necessary to tenfold (ten thousand) and added to the original amount (total: one hundred ten thousand rubles).
If to add to the amount of interest you decide to use any calculator, do not forget that in Windows there are apps of this kind. Run it through the main menu on the "start" button - in the menu go to "All programs", then to "Standard", then in the section "Service" and choose "Calculator". Although you can not go so far, and press the key combination win + r, calc score and click on the "OK" button. C using a calculator, you can solve this puzzle in several ways. For example, enter the original amount, click the division button, enter 100, then click multiply and enter the amount of interest. Then click on the summation and re-enter the original amount and then press Enter. The number in the window of the calculator will be the amount with the added interest.
If you trust to calculate the amount of added cent the Internet, then it can be done even from your mobile phone. Go, for example, search engines such as Google and specify in the search query box of the desired mathematical operation. For example, if you need to add to the original amount of one hundred thousand is 10%, enter this search query: "110% of 100000". The mighty intellect of a search engine will immediately calculate and present the results to you.