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03.26.2018: One Chapter of Math

Today's soundtrack is Wolf Alice: Visions of a Life.

This afternoon, I'm on Chapter 13 of Basic Math & Pre-Algebra For Dummies, "Word Problems With Fractions, Decimals, and Percents."

The chapter begins by discussing word problems that involve adding and subtracting fractions, decimals, or percents. The first step, of course, is to break the problem down: convert it from a word problem into an equation, then calculate it.

To work out a word problem with fractions, decimals, or percents that says "of," recognize that "of" means "multiplied by," then figure out what you need to multiply by.

To solve a problem that requires you to find how much you started with before removing x % and gives you the end result, first subtract the removed percentage from 100%, then divide the result by the end answer to get the missing first link. The example given in the book looks like this: Maria got some birthday money. She put 40% in the bank, spent 75% of the rest on a purse, and had $12 left over. How much did she start with? So I would say 12 / .25 = 48, and 48 / .6 = 80; therefore, Maria was given $80 for her birthday.

To add a percentage to a number, we simply convert the percent to a decimal, add 1, and multiply the result by the desired number: For example, a 5% raise on a $30,000 salary looks like this: 30,000 x 1.05 = 31,500, so the answer is $31,500.

To calculate a discounted percent of an amount, first take 100% and subtract the discounted percentage, then convert that result to a decimal, and multiply the decimal by the original amount. For example, to find out what the final cost of an item listed at $30 with a 25% off discount, take 100% - 25% = 75%; 0.75 x 30 = 22.5; thus, 30% off of an item listed at $30.00 would bring the item's price down to $22.50.


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