## Thursday, December 12, 2013

### Austin's Percent Post

Hi! Do you like math? You probably don't because you're a boy. But girls are smart so maybe they will actually view my percent post!

A Introduction to Percents.
1.
a) To find 50% of any number you simply just divide that number by 2 and you get 50% of that number.
b) To find 10% of any number you have to divide that number by 10 in order to get 10% of that number.
c) To find 1% of any number you have to divide that number by 100 to get 1% of that number.
d) To find 25% of any number you have to divide that number by 4 to get 25% of that number.

A percent means out of 100 or another name for hundredths.

Percents Represented in 100 Grids.
2. If you don't have access to a 100 grid just trace out a 100 grid from grid paper.

180%

12 3/4%

0.7%

Changing Decimals to Percents to Fractions.
3.
a) To change 26% to a decimal, take the decimal in 26.% and move the decimal two spots to the left so you will end up with 0.26. 0.26 will be your decimal.To change 26% to a fraction you have to take the decimal, 0.26, and you use the place value of your smallest digit, which is 6 hundredths, to create your denominator. So far you will have ?/100. Once you have the denominator you need to take your number and make it your numerator. Your fraction will 26/100.

b) To change 7/10 to a decimal, you need to divide the numerator by the denominator so you will get 0.7. To do this with out a calculator you have to remember /10=.0, /100=.00, and so on. You just take the numerator and place it on the tenths place value so you get 0.7. To change 7/10 into a percent you have to take the decimal and you move the decimal 2 spaces right so you end up with 70.%.

c)To change 0.024 to a fraction you have to take your smallest number which is as of now 4 thousandths, and use the place value as your fraction. So far you will get ?/1000. To get the numerator you have to take your number and use it as a numerator and remove the zeros. Your fraction will be 24/1000. To change 0.024 into a percent you have to take the decimal and move it two spaces to the right. Your percent will be 2.4%.

Finding Percents using Mental Math and Calculators.
4.
20% of 60
To find 20% of 60 with a calculator you have to divide 20% by 100 so you'll get 0.2. Take 0.2 and multiply it by 60 (0.2 x 60) you will get 12 as your answer.
To find 20% of 60 with out a calculator you need to find 10% of 60 that is pretty easy because you already know that 6 x 10 = 60 so 10% of 60= 6. You take 10% of 60, which is 6, and add another 10% to get your final answer that is 12.

0.1% of 40
To find 0.1% of 40 with a calculator you have to divide 0.1 by 100. You will get 0.001, you take 0.001 and multiply that with 40 (0.001 x 40=) to get 0.04. To do this with out any calculators you can simply divide 40 with 100 (40/100) and you will still get the same answer.

250% of 400
To find 250% of 400 with a calculator you have to divide 250% with 100 to get 2.50. Take 2.50 and multiply it with 400 (2.50 x 400) and you will get 1000 as your answer. To solve this with mental math you know what 100% of is that 400, the question is asking you for 250%. If you break it up you should get 100%, 100%, and 50%, since you have the knowledge of 100% of 400 is 400 you just add up
400 + 400= 800. You're not done yet, you still have to find 50% of 400. How do you find 50% you say? Well you have to remember that 50% is = to a half so you just half 400 to get 200. Finally you take 200 and add it to 800 (800 + 200 = 1000) your final answer will be 1000.

Combining Percents, Finding Discounts, Prices, and Tax Prices.
5.
Lets use this question as an example. A door mat is on sale for 40% off, the original price is \$100, what is the the total price of the door mat with tax?
PST=7%
GST=8%
First we need to find out the discount price first before we find the total cost. Finding 40% of 100 is pretty easy but if it would any other number you would do 40/100 to get 0.4. You would then take 0.4 and multiply it by 100 (0.4 x 100) to get \$40. You can take 40 away from 100 (100-40= 60) to get \$60.
That is only your discounted price, you now have to find the final cost with tax. To find the tax you have to take your tax of 15%, the PST and GST combined, and divide it by 100. You will get 0.15 eventually and so to find the tax you take your discounted price and multiply it by 0.15 ( 0.15 x 60 = 9) your tax will be \$9. To find the total cost you take your tax and add it with your discounted price to get \$69. You can apply this strategy to any number.
Here is a outline of what I just did.
1. Find the discount price.
2. Find the tax price.
3. Calculate the final cost.

Here is another example question. Which is a better deal 50% off or 25% off of an already reduced price of 25%?

To solve a question like this one you have to take any number especially something you can work with easily like 100. Using mental math strategies we can easily figure out that 25% of 100 is 25. Taking away 25 from 100 (100 - 25 = 75) will end up with 75. This is where you have to use your calculators because we have to find 25% of 75, which is pretty difficult, so you would just divide 25% by 100 (25/100) to get 0.25. take 0.25 and multiply it by 75 (0.25 x 75) to get 18.75 or you can just divide 75% by 4 to get the same, exact number. To find 50% of 75 isn't very difficult because you are just halving 75 to get 37.5. Take 25% of 75 that is 18.75 and take 50% of 75 that is 37.50 and just subtract them with 75 ( 75 - 18.75 & 75 - 37.50). Once you have calculated the numbers you will 75 - 18.75 = \$56.50 and 75 - 37.50 = \$37.50, just by looking at them you can easily tell that 50% of an already reduced price of 25% is much of a better deal. If you are really lazy or do not want to read my explanation you could just eyeball the percents and you can easily tell that the higher discount has the lower price.

Here is helpful video that shows some strategies on how to find percents.