Pre-Algebra: Chapter 9-5
Using the Percent Proportion
We know how to convert fractions to percentages. Remember D2P, it stands for decimal to percentage.
To convert from decimals to percentage, we move the decimal from left to right 2 decimal places.
To convert from percentages to decimals, we move the decimal point 2 decimal places from right to the left.
Finally, we can use wickity-whack divide, a BOX with Number (3), percent %, of and 100. No matter what kind of problem, we have with percentage, we can use this method to solve the problem. Here is an example BOX that you can practice with! Remember to criss-cross!
Algebra: Chapter 10-5
Addition and Subtraction with Unlike Denominators
This lesson is TOUGH and takes time to do right. We have to bring all of our tools to the problem. Know how to FOIL, recognize binomial squares, and use the BOX method of FACTORING ACCURATELY.
Unlike Lesson 4, we have differing denominator terms and we must find a common denominator of both rational expressions.
Given that p, q, r and s are rational numbers or expressions, the easiest way for addition and subtraction is with this equation: (p÷q) + (r÷s) converts to become (ps + rq) ÷ qs for addition or (ps – rq) ÷ qs for subtraction.
Sometimes, we need to find the LCM (least common multiple of the denominators. These steps will help:
- Factor each expression
- For the product using each factor the greatest number of times it occurs.
Just go slow and be methodical. SHOW ALL THE WORK and you’ll be fine, try shortcuts and you’ll regret it.
Purplemath has a good explanation and plenty of examples here too. Just make sure to scroll down to the middle of the page and the next page as well.