Curtis’s Speed GED » Mental Math

GED Math: Taking a Closer Look

Curtis — Tue, 10 Nov 2009 02:14:43 +0000

S’up y’all. Ready for some more GED Math?

I been thinkin’ about how sometimes we think we know the answer without looking at the whole problem, you know? Check this out.

Super Subs Inc. is planning on hiring new employees for the summer. They want to make sure their new employees are available to work on the busiest day of the week. Below is a chart of their four different stores, and how many sub sandwiches they sold at each store the previous week. According to this chart, which day will the new hires most likely need to work?

1. Wednesday

2. Thursday

3. Friday

4. Saturday

5. Sunday

I usually like takin’ short cuts, right? But you can’t depend on short cuts. You gotta make sure you’re right, or you’ll get taken for a ride.

First, we gotta make sure we know what we’re lookin’ for. The question’s askin’ what day is most important for new employees to work. The most important day is when they’re sellin’ the most, right? So, next thing is to check out is on which day they’re sellin’ the most subs. When I first look at this chart, I just scan through and see that in the first row, for store “A,” they’re sellin’ the most on Friday. Bam, that’s the answer, right? Wrong. Scannin’ a chart real quick is a good strategy to get information, but you always gotta double check. Check out stores B-D. They’re sellin’ more subs on Saturday. Since there’s three stores that sell more on Saturday, and only one that sells more on Friday, now we can make a better guess that Saturday’s the answer we’re lookin’ for. But let’s double check again to make sure.

Add up all the subs sold on Friday at all the stores. It’s 489. And Saturday is 560. In fact, you don’t even need to really add all those up straight up, you can just estimate and get 490 for Friday and 570 for Saturday. See, we were right, even with simple estimation, we can see they sell way more subs on Saturday. Since we scanned first, then double checked, we can be sure we got the right answer now. It’s 4. Saturday.

So check out this next question.

Super Subs Inc. may need to shut down a store due to the bad economy. According to the chart, which store would they most likely shut down?

1. Store A

2. Store B

3. Store C

4. Store D

5. None of the Stores

Remember, we can’t just take a guess lookin’ at the first column of numbers. What y’all think the answer is?

For more information about the GED test and GED test preparation, visit the GED Academy at http://www.passGED.com

Adding Mixed Fractions and Estimation

Curtis — Mon, 11 Aug 2008 01:14:53 +0000

Valerie said:

hi all need adding mixed fractions please.

and:

Hi curtis its valerie in florida again new question wow took the tape test and im ready to do the GED in Reading wow ok in math the total score was 5.0 G.E that she said had to get to 10.0 right ok she said to start in Estimation what is this rounding off ? please tell me what to do where to go in the ged study video ty.

Hey there, Valerie! First off, congrats on bein’ down with the reading. That’s one more done! Now, the math…

Estimating

Estimation is rounding off, like you said. But it’s also part of what I call mental math. In the passGED study program, you can go to the first math course (Learning about Numbers), and go to Unit 1, Lesson 6, to learn all about it. I call it mental math. You can estimate to make your job on the GED a lot easier, so you don’t have to do so much math. That means, goin’ through a problem an’ figuring out about what the numbers are, in round numbers that’re easy to work with. With multiple choice answers, if you figure out about what the right answer is, you save a lot of time. You don’t have to get it exact.

Say, I got a problem:

5,890 + 8,799 + 2,014 + 9,882 + 4,649

Okay, that’s gonna take a little time to work out on paper, but I also got some multiple choice answers:

A) 35,892

B) 31,234

C) 29,449

Can I figure it out without goin’ through all the math? Prolly. Here I go…

5,890 is about 6,000, and 8,799 is about 9,000, and 2,014 is about 2,000, and 9,882 is about 10,000, and 4,649 is about 4,500… so the question is ABOUT

6,000 + 9,000 + 2,000 + 10,000 + 4,500 which is ABOUT

6 + 9 + 2 + 10 + 4-1/2 thousand.

That’s like 6 + 9, is 15, plus 2 is 17, plus 10 is 27, plus 4-1/2 is 31-1/2…

So, it’s about 31,500. That’s pretty close to answer B. So that’s my choice. If you figure it out on a calculator, that’s it. See how good that can be savin’ you time on a test?

Adding Mixed Fractions

Fraction Basics…

Befo’ starting about fractions, here’s the link to all my articles on fractions… http://www.passged.com/student_blogs/curtis/category/fractions/

You gotta start by really lookin’ at what a fraction is… I mean, you got two numbers in a fraction, right? One on top an’ one on the bottom. Like, 1/2… that’s an easy one to think about. The top number (1) is called the numerator, and the bottom number (2) is called the denominator. But that’s not the point. Remembering what they’z called is jus’ to help you understand what math books is talking about. What’s really important is what they mean. Think about a pizza. It’s divided in half. Each half is 1/2, right? That’s basic. The top number (1) is really the number of parts you have, and the bottom number (2) is the number of equal parts the whole thing is divided into. That make sense? So you got 1 part out of 2 parts… then, you got half.

Same thing if you got 3/4… say you got 3/4 of a box of candy. That means, if you divide the box into 4 equal parts, you got three of them. What happened to the other 1/4? Who knows? Maybe someone ate it.

So, if the whole box of candy originally had 16 chocolates in it, and you got 3/4 of the box, how many chocolates you got?

Now, there’s a GED math question for you… this is also called a ‘ratio,’ but really if you understand what fractions are, it’s pretty easy.

Say you got 16 chocolates, and you wanna divide it into 4 parts (see, 3/4 means its divided into 4 parts, right?) Then, you divide 16 by 4, and you get 4. See, 4 piles of 4 chocolates each is 16 all together… and each pile of 4 is 1/4 of all the chocolates. Hey, get 16 chocolates (or paperclips or anything) and give it a try. No way to learn like actually seeing it, right?

So if you got 3/4 of the chocolates, then you got 3 of the 4 piles. So, you multiply the number of chocolates in 1 pile (4) by the number of piles you got (3) to get the total number of chocolates you got… 12. D’you follow? Here it is in math terms:

How much is 3/4 of 16? (Of usually means multiply, so…)

3/4 x 16 = 3 x (16 Ã· 4) = 3 x 4 = 12

So, if 2/6 of the 24 people in your office vote to have hamburgers for lunch, how many people voted to have hamburgers for lunch?

2/6 x 24 = 2 x (24 Ã· 6) = 2 x 4 = 8

See how it works? If you divide 24 people into 6 equal groups, there are 4 people in each group. An’ if 2 groups vote for hamburgers, that’s 8 people.

Now on to the real question…

Adding Mixed Fractions

Mixed fractions is when you got a whole number like 3 plus a fraction like 3/4. So, if you’re addin’ mixed fractions you got something like this:

1-4/5 + 6-2/3

Problem is, it’s hard to add two fractions that have different bottom numbers. It’s like I was sayin’, if you have one set divided into 5 equal groups, and another set of things divided into 3 different groups, the groups will be different sizes. So, it’s like apples and oranges. You can’t add ‘em together.

So, you gotta figure out the smallest number that can go at the bottom of the fraction to make both fractions have the same bottom number. Well, a lot of the time, that number is the two denominators (bottom numbers) multiplied together. And that’s the case here. You can change both fraction to something-15ths.

4/5 = ?/15

This is jus’ like I was talking about before. Say you got a box of 30 chocolates, divided into 5 groups. Then, you got 6 chocolates in each group, right? And 4/5 of the chocolates would be 24 chocolates. (4 groups of 6 chocolates).

Now, what if you divide the chocolates into 15 groups? How many groups make up 24 chocolates? Well, if you divide 30 chocolates into 15 groups, you got 2 chocolates in each group. And 12 groups makes up 24 chocolates… 12 groups of 15 is the same as 4 groups of 5.

4/5 = 12/15

There’s a shortcut way to figure it out… because 5 x 3 is 15, you multiply the top number by the same thing (3) to get 12 on top. This always works! So…

2/3 = ?/15
since 3 x 5 = 15…
2/3 = (2 x 5)/15 = 10/15

Okay, now you got your numbers the same at the bottom….

1-4/5 + 6-2/3 = 1-12/15 + 6-10/15

Next step is to add the whole numbers and add the fractions. When you add fractions, just add the top numbers (12 groups plus 10 groups is 22 groups, no matter how big the groups are, right?)

1-4/5 + 6-2/3 = 1-12/15 + 6-10/15 = 7-22/15

Now, 22/15? If the top number’s bigger, then you got more than one. 15/15 is a complete set of groups… so it’s 1. That means, 22/15 = 1-7/15. So…

1-4/5 + 6-2/3 = 1-12/15 + 6-10/15 = 7-22/15 = 8-7/15

Hope this helps!

GED Math Question S. Sain-Mellner

Curtis — Mon, 10 Mar 2008 19:43:27 +0000

Here’s a good question ’bout the GED math test… everyone wants to know how to pass. That be the bottom line…

Out of what 50 questions on the math test how many should i get right just to be safe in order yo pass? Also what sections should i study on the most?

Sincerely,

S. Sain-Mellner in Virginia

The GED don’t really go by how many questions you get right. They see how good you do against all the other people takin’ the test. So, it all depends on the version of the test you get. Stinks, right?

To really know you gonna pass, though, try to get 35 out of 50 right. But you may be okay with less, depends on how good you do on the other tests and how hard the test is. To be sure, go for the 35 right…

Now, what to study most? Best thing to study is basic math. Practice doin’ word problems, and doin’ math in you head. The reason is, this is gonna help you on all the math questions. The harder stuff’ll help you with one or two questions, but practicin’ word problems and doin’ math faster in your head (mental math) is gonna help the most with all the questions. Here’s some places to go for word problems:

http://mathforum.org/dr.math/faq/faq.word.problems.html

http://www.studygs.net/mathproblems.htm

http://www.how-to-study.com/solving-math-word-problems.htm

And here’s some places to go for mental math:

http://io.uwinnipeg.ca/~jameis/Math/D.mental/DEY1.html

http://mathforum.org/t2t/faq/faq.tricks.html

http://blog.thembid.com/index.php/2007/07/14/do-math-quickly-in-your-head/

For more information about the GED test and GED test preparation, visit The GED Academy at http://www.passged.com.

GED Question from Mark: Changing Fractions to Decimals

Curtis — Mon, 10 Mar 2008 19:23:16 +0000

Yo. Here’s a good question from Mark about somethin’ that’s real helpful for the GED: mental math. That’s doin’ math in your head. And it makes the GED math test easier and faster.

I used to work in a machine shop. Sometimes I would have to convert fractions to inches like 1/3. I know how to do that, all you have to do is divide 1 by 3. The question is, I always had to use a calculator, and I would like to do that without using a calcualtor. Every time I tried I would’nt get the proper answer. How do you do that without using a calculator.
Mark

Yeah, that’s the key, Mark. Doin’ stuff in your head makes it easier and faster, an’ helps a lot on the GED. Part of it is jus’ knowin’ or rememberin’ some of the fractions you see all the time.

Think of it in terms of dollars and cents to remember the real easy ones:

1/4 (a quarter) = 25 cents or .2

1/2 (half dollar) = 50 cents or .5

3/4 (three quarters) = 75 cents or .75

1/10 (a dime) = 10 cents or .1

Tenths are easy. It’s always gonna be point-whatever-is-on-top:

2/10 = .2

3/10 = .3

4/10 = .4

5/10 = .5

6/10 = .6

7/10 = .7

8/10 = .8

9/10 = .9

Fifths is always point-the-top-number-times-2.

1/5 = .2

2/5 = .4

3/5= .6

4/5 = .8

Then, there’s the thirds. These are pretty easy to remember, but they don’t give even numbers:

1/3 = .3333 (remember the 3 from 1/3)

2/3 = .6667 (remember that 2 x 3 = 6)

Then, there’s eighths.

1/8 = half of a quarter = .125 (you can remember it cuz 12 is kinda like 1/2 and 25 is a quarter)

2/8 = 1/4 = .25

3/8 = 1/8 + 2/8 = .125 + .25 = .375

4/8 = 1/2 = .5

5/8 = 1/2 + 1/8 = .5 + .125 = .625

6/8 = 3/4 = .75

7/8 = 3/4 + 1/8 = .75 + .125 = .875

Then, what about more complicated ones? You can still do ‘em in your head. You gotta divide the bottom number into the top, so like 2 into 1 = .5 … on harder ones, it’s harder to do in your head.

Say you have 11/25 … you gotta divide 25 into 11… Start by adding a zero to the 11. So you got 25 into 110… 25 goes into 100 four times, so you got a 4… and ten left over. Add another zero… and that’s 25 into 100 again… that’s 44. Now, where’s the decimal go? Well, it’s before the first number, .44 … you can check it by thinking, 11/25 is almost a half, and .44 in almost .5. So you’re good.

Another way is to try to make the bottom number 100. So, 11/25 = 44/100. Then you take the top number and move the decimal place 2 points, so 11/25 = .44

Here’s some places to go for some more explanation and practice:

http://www.mathsisfun.com/converting-fractions-decimals.html

http://www.curiousmath.com/index.php?name=News&file=article&sid=77

http://www.learningwave.com/chapters/decimal13/basics/convert.html

http://www.coolmath.com/decimals/04-decimals-converting-fraction-to-decimal.html

For more information about the GED test and GED test preparation, visit The GED Academy at http://www.passged.com.