Construction MathSection 6:Conversion Process

Part 1: Decimals and Percentages

Two parts to the word◦ “per” indicates division, miles “per” hour, dollars

“per” hour (ok, so it’s not really worded this way commonly, but this is really how your hourly wage is broken down)

“cent” indicates 100◦ “cent”ury 100 years◦ 100 “cent”s to a dollar◦ 100 “cent”imeters in a meter (link to next week,

hint, hint, wink wink)

Percent Vocab Check

So a percent literally means “out of a hundred” (literally “per a hundred”, but out of a hundred sounds more modern)

So, we need to figure out how to represent parts of 1 in terms of 100 (parts of a whole)

Divide 1 into 100 (now we should have hundredths)

so, when dealing with percentages, we will represent them as decimals

Percentage Vocab

How do I represent 25% as a decimal?◦ 0.25

We divide 25 by 100 Or we simply move the decimal to the LEFT twice. If

you are having trouble remembering which way to move the decimal, focus on multiplying and dividing. This is NOT a step you want to make a mistake on. Remember, decimal errors can kill

Quick Examples

If we divide by 100 to convert percentages to decimals, what should we do to convert decimals to percentages◦ PD

divide by 100 Or move the decimal point two to the left

◦ DP Multiply by 100 Or move the decimal point two to the right

Converting the other direction

Convert these decimals to percentages◦ 0.62

62%◦ 0.475

47.5%◦ 0.7

70%◦ 3.3

330%◦ 1.3

130%

Test your skill

Convert these percentages to decimals◦ 72%

0.72◦ 12.5%

0.125◦ 150%

1.5

Test your skill

You need to lay flooring in the living room/dining room. The customer wants tile in the dining area and carpet in the living area. The room is approximately 200 square feet, and the dining area should take up about 30% of the total area. How much tile will you need? ◦ 60 sq ft

30%0.30 0.30 x 200 =60

Construction application

You decide you want an iPad, and need to find out if you can afford it. The one you want costs $699, but you found a site that can offer it to you for 25% off. You have saved $500 from Christmas and birthday and chores. Can you afford it on sale?◦ 25%0.25◦ 0.25 X 699=174.75◦ 699-174.75=524.25◦ Nope.

Real-life application