# Posts Tagged: "proportions and percents"

## Compound Interest

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In simple interest computation, interest is computed based on the invested capital over the period of time at stated interest rate.

If at given intervals over the whole term of the investment, the principal due is added to the original principal and subsequently grosses interest, the amount by which the original principal has increased by at the conclusion of the term of the investment is called compound interest. The total amount due which comprises the original principal and the compound interest is called the compound amount. Lastly, the time between successive conversions of interest into principal is called conversion period. This implies that under compound interest method, interest earns another interest.

## Simple Interest

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Interest is an income derived from an invested capital or the amount of money paid for the use of someone’s money. Computation of interest employs the application of finding percent of a quantity since the interest on investment or debt is usually a certain percent of the capital or amount loaned over the whole term of the investment or obligation. Simple interest is the interest which is computed on the original principal during the whole time, at the stated interest rate.

To compute for simple interest, multiply the principal, rate and time (expressed in years or a fraction thereof). The sum of the interest and the original principal or amount borrowed is the amount or future value of the investment/obligation.

## Similar Figures Word Problems

- - Pre-Algebra

Similar figures and scale drawings are very useful topics in mathematics and in many other subjects. In social sciences, for instance, students are provided with maps of diverse countries and cities all over the world. The students must be able to interpret the maps in order to comprehend them. Proportions provide students an idea of what a scale is. Scales are obtained from a scale factor. A figure may be tightened in any direction by a certain scale factor, which then makes the resulting figure similar to the original.

## Similar Figures

- - Pre-Algebra

Two figures are similar $\left(\sqcup\right)$ if they have the same shape but not necessarily the same size. In geometry, if two figures are similar, the ratios between the lengths of their corresponding sides are equal. To determine whether or not two or more figures are similar, we establish a comparison between the lengths of their corresponding sides.

Corresponding sides of any two figures are those that directly relate to each other. If their ratios are equal, the figures are similar.

## Proportion Word Problems

- - Pre-Algebra

After learning proportions, let us now try to solve word problems involving proportions. To do so, we form the proportion between the ratios given in the problem then solve for the missing value by applying the property between its means and extremes.

## Proportions

- - Pre-Algebra

Equal or equivalent ratios form a proportion. Proportion states the equality of two or more ratios. Proportions can be written in ratio form or in rational form. The proportion $\frac{2}{3}=\frac{6}{9}$ can also be written as $2:3=6:9$. Usually, a proportion involves four numbers where the end (outer) numbers are called extremes while the inner (middle) numbers are called means. In the given proportion above, the extremes are 2 and 9, while the means are 3 and 6.

In proportion, the product of the means is equal to the product of the extremes. To determine whether or not a given pair of ratios will form a proportion, one can check if the product of the means would equal to the product of the extremes.

## Markup, Discount, and Tax

- - Pre-Algebra

On some occasions, when you go to a department store you probably have seen signs like: 10% off, 20% discount or buy 1 get 1. These signs are placed on items under bargain sales, which oftentimes come as the store’s strategy on top of promotion, closing or clearance sales. In fact, some of us are even taking advantage of this chance.

Before learning how to compute markup and discount, let us be familiar with some business terminologies such as markup, marked price, discount, discount rate, and selling price. Markup refers to the difference between the selling price of an item or service and the total cost of the item, including the operational expenses and the cost incurred in buying the item. In other words, markup is actually the profit per item. It can be a fixed value or a percentage of the total cost. Selling price, also known as the net price, refers to the price of an item, good or service after all deductions has been made. This amount of reduction is known as the discount and when stated in percent is now referred as discount rate.

## Percent Change

- - Pre-Algebra

If one wishes to make a comparison between two or more variables; he may describe how one value is affected by a change in the value of the other variable and vice versa instead of just giving the values and get their difference. Precisely, to denote rate of change is to write it as a ratio or percent with respect to the original value.

For instance, you are interested in comparing the first two yearly sales of an enterprise from the start of its operation. Knowing the corresponding sales for the first two years does not necessarily give a clear picture about their relationship. It is more precise to say that the yearly sales has increased or decreased by certain percent. We call this percent as percent change. Percent change refers to the percent increase or percent decrease or the degree which something either earns or losses a value.

## Percent Problems

- - Pre-Algebra

The word percent came from the Latin word “per centum” which means every hundred or fraction of a hundred. Percentage is the result when taking a certain percent of a number. For instance, you are asked to find 20% of 50. This means if 50 is divided into 100 equal parts and you take 20 parts of those, what is the result?

## Converting between Fractions, Decimals, and Percents

- - Pre-Algebra

Percents are widely used in business and everyday life. Business professionals use percent to calculate percent of loss or profit, and percent of increase or decrease in transactions such as sales, cost and expenses. Retailers and dealers use percent to give discount to their customers. Consumers are concerned with the percent of change of prices while employees are worried with the percent of their salaries paid in taxes.