Posts Tagged ‘cross multiplication’

Finding Percents

Tuesday, September 15th, 2009

How to Find a Percentage of Any Number

YouTube Preview Image

Description

A detailed tutorial on the finding of percentages of any number. Step by step tutorial including several examples of how to find percents for reference.

Overview

The knowledge of how to find percents isn’t just something you’ll find in the classroom. You’ll find it all over for the rest of your life – at home, at work, even at the grocery store. Finding percents is a very important skill. It can be very confusing to be faced with some percent of a number that isn’t 100. Thankfully, it is very easy to solve, with the help of cross-multiplication. Cross-multiplication is setting up two fractions and multiplying them in an x formation. One of your fractions will be the percent – a number over 100 – and the other fraction will be an unknown variable over the number you need to find the percent of. After using cross-multiplication, just solve for the unknown variable. The video provided shows a second method to solve percents with.

Tags: , , , , , , , , ,
Posted in Algebra | No Comments »

Cross Multiplication

Thursday, September 3rd, 2009

How to Solve Problems Using Cross Multiplication

YouTube Preview Image

Description

This video gives an example of how to solve proportions using the cross-multiplication technique. Several examples are provided as well as easy to follow step-by-step instructions. This video also provides sample word problems, with examples of how to use the cross-multiplication technique with word problems.

Overview

Cross multiplication is often used with fractions and proportions, and is found in many word problems. A cross multiplication problem will normally have two fractions set equal to each other, with one fraction complete, and one fraction with one variable in either the numerator or the denominator. Take the numerator of the first fraction and multiply it by the denominator, then set it equal to the denominator of the first fraction multiplied by the numerator of the second fraction. An example is x / y = a / b. You would change this to x * b = y * a. From there you can simply solve for the variable.

Tags: , , , , , ,
Posted in Algebra | No Comments »

Ratios & Proportions

Thursday, September 3rd, 2009

How to Write and Solve Ratios & Proportions

YouTube Preview Image

Description

This video gives an introduction to ratios and proportions. Included are several examples of each, and a quick tutorial on how to make more ratios from one ratio that you are given, which will create a proportion. 

Overview

Ratios, while used in basic math, is most commonly used in statistics. The number of something to the number of something else is used very often to illustrate the different between something. There are three different notations for this – X to Y, X:Y, and X/Y. They all mean the same thing and are all in the same order. Proportions can be thought of as two ratios measuring the same thing. Sometimes, one of these will have a variable, an unknown quantity. Proportions like this can be solved using cross multiplication, and can often be found in word problems.

Tags: , , , , , ,
Posted in Algebra | No Comments »