Monthly Archives: October 2011

Dealing with Decimals

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I think a great way to understand what decimals are is to put decimals into a table. As you can see from the table below, decimals can be written in many ways. One example of this is the number 0.1 can be written as 1 tenth, 10 raised to the -1, or 1/10. Decimals are base-ten units; therefore, we use the unit ten in the table.

The United States separates numbers with commas every third number:  5,853,567.75; however, many other places around the world separate their numbers with spaces and use a comma the way the United States uses the decimal point like this 5 853 597,75. I think this is a very interesting fact! Another thing I learned is that the number 0.0000000009 is easier to read if we put spaces every third number: 0.000 000 000 9. If we put spaces it does not mean anything different; it is just to help us count the zeros or read the number easier. These are great tips to keep in mind while working with decimals.

As you can see from the decimal table, decimals can be written in many ways; essentially a decimal is a fraction. I say this because 0.732 is 732/1000 and can be written as 732 thousandths.  Another example of this is 0.20 is 20/100 and can be written as 20 hundredths. No matter the decimal number it can always be written as a fraction which may be easier for some people. You can also look at a decimal by expanding it. If we look back at the decimal 0.732 we can break it down into three parts 0.732=0.7+0.03+0.002. This can also be written as 732/1000=7/10+30/100+200/1000. Decimals are very versatile which allows for many different strategies to understand them better!

Digging Deeper into Fractions

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Did you know fractions are easier to picture in your head if you estimate? I have learned from experience that fractions truly are easier if you use estimation. An example of this is 7/8 + 1/3, this may look tricky if we actually were to work out the problem and find the same denominator. If we were to attempt this problem using estimation, we could say that 7/8 is almost equivalent to 8/8 (1), and 1/3 is a little larger than 1/4. If we add 1 +1/4, the answer is 1 1/4. Although this may not be the exact answer, it gives us a good idea of what the fraction will be. This is an easy way to compare fractions and gain a better understanding of them!

Another great way to help gain an understanding of fractions is by using fraction bars. Fraction bars are rectangular shaped pieces of paper that are divided up into different amounts. The different amounts are the fractions that the shape equals. For example, I have 5 different fraction bars: twelfths, sixths, fourths, thirds, and halves. The rectangles that represent twelfths are divided into 12 sections; the rectangles that represent sixths are divided into 6 sections, and so on. These are great tools to work out fraction problems. Finding a fraction between 2/6 and 3/6 is easier with fraction bars. This may sound easy, but it is hard to figure out if you do not have a good understanding of fractions. Let’s use fraction bars to help us out; for starters we will need a 2/6 fraction bar and a 3/6 fraction bar. If we set these fractions bars side by side, we can easily see that 5/12 is between both 2/6 and 3/6. I found this by looking for a fraction bar that was in between 2/6 and 3/6.

When dealing with whole numbers and fractions, it is easier to set them up into improper fractions. To set up an improper fraction you need to multiply the denominator by the whole number and add the numerator. We do this because we are essentially looking for a common denominator. An example of this is 4 1/2, we start with 2(denominator) x 4(whole number) = 8, then we add 1 (numerator) = 9/2. 9/2 is an improper fraction because the numerator is larger than the denominator. We can also find the improper fraction by finding the common denominator. 4 1/2 can also be written as 4/1 + 1/2; in order to find the common denominator we need to multiply the 4 by 2. Once this is done we can add the two fractions together which gives us the sum of 9/2. This idea is helpful when adding and subtracting fractions: 1 2/3 = 5/3 – 1/3= 4/3. Take your time to learn fractions because I think it is a great tool that we can use in our daily lives.

Learning Fractions

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Fractions can be confusing and hard to understand. It can be easy to misread or do a problem wrong that is dealing with fractions. For example, in the problem 5/3 +3/3 many may get confused and say the answer is 8/6. This is wrong because you cannot add two like denominators in the problem. Denominators are the numbers on the bottom of the fraction; in this case the denominator in 5/3 and 3/3 is 3. It is less likely to get confused if 5/3 is written as 5 thirds and 3/3 is written as 3 thirds. Clearly, you can see that the denominator is going to stay 3 or a third. You do not add the denominators (3+3=6) because that is not correct. This is a nice tip to follow especially if you are teaching younger students who have never dealt with fractions before.

Another great tip to help learn more about fractions is having the same unit. For example, if you have 2 yards + 9 feet you cannot add them because yards and feet are not the same unit. In this case you would have to convert one of the units in order to make them both have the same unit. You can do this two different ways with the example provided: yards can convert to feet and feet can convert to yards. Let’s convert 2 yards into feet. In order to do this we must know how many feet are in a yard, which is 3. So if there are 3 feet in a yard and we have 2 yards that means there are 6 feet in 2 yards. Now we can do the problem! 6 feet +9 feet = 15 feet.

I found that drawing measuring cups helps to understand the conversions between halfs and fourths.  For example, if we have 3 halfs + 1 fourth it may be confusing to solve the problem if you don’t have something to look at. First of all we need to convert either halfs to fourths or fourths to halfs. I am going to solve the problem by converting halfs to fourths because a fourth is smaller than a half. I have included a picture of measuring cups to work out the problem. The end result is 6 fourths + 1 fourth= 7 fourths.

Investigating Integers

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The word integer may seem a bit simple, but as I have learned it can actually be tricky to understand. The first thing that one must know about integers is that the number can be either positive or negative. For example, a set of integers looks like this: {…-3, -2, -1, 0, 1, 2, 3…}. This shows that the negative numbers will continue infinitely as well as the positive numbers. Once the idea of integers is understood, adding and subtracting begins.

A simple way to understand the meaning of an integer is to name the number n. So if n=the number, -n=the opposite of the number, and -(-n)=the opposite of the opposite of n. The opposite of the opposite of n would simply mean the number is positive. An example of n+n is 2+2=4. In this example there are two positive numbers which result in a positive answer. An example of -n+n is -2+2=0. This shows that 2 negatives plus 2 positives cancel each other out resulting in zero. An example of -(-n)+n is -(-2)+2=4. In this example the -(-2) is equivalent to 2, so when we add 2+2 it equals 4.

A great hands on activity that helped me to understand integers was using color counters. Color counters are little square shapes; one side of the square is red and the other side is black. The red side stands for the negative integer and the black side stands for the positive integer. For example to show 2+2=4, you would have 4 black color counters. The example -2+2=0 you would have 2 blacks and 2 reds, which cancel each other out. To show -(-2)+2=4 you would simply have 4 black color counters like in the example 2+2=4. The picture provided is a great representation of the examples I have explained.

Grasping the Greatest Common Factor

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It feels like just yesterday I was learning about greatest common factors in elementary school. The only difference from learning GCF’s now is that I actually understand it. The greatest common factor is the largest possible number that can divide into a set of numbers equally. An example of this is find the GCF of (24,36), the answer is 12 because 12×2=24 and 12×3=36. There are no larger numbers that divide equally into 24 and 36.

Although the example GCF(24,36) is simple, there is a trick for the more complex problems. For example find the greatest common factor of (2100,3360) seems almost impossible, but I have learned a trick to help speed up the process. Instead of plugging numbers into your calculator you simply need to draw a factor tree for both numbers. The picture provided is what the factor trees should look like.

Once you have the factor trees drawn, you write out the prime numbers for 2100 and 3360. The prime factors of 2400 are 2x2x3x5x5x7, and the prime factors of 3360 are 2x2x2x2x2x3x5x7. The trick to finding the GCF of the 2100 and 3360 is to look at the intersection (overlap) of the numbers. The numbers in read are the overlap (2x2x3x5x7). After you find the intersection, you need to multiply the numbers together (2x2x3x5x7=420). This means that the greatest common factor of 2400 and 3360 is 420. This may look like a lot of work, but it is actually much less work than using your calculator to guess and check numbers.

Facts about Factors

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Factors can be intimidating, but there are some tricks that help to understand them. Factors are numbers that are multiplied together to equal the final number. For example in the problem 2×4=8, the factors are 2 and 4. Although these are factors, they are not prime factors. Prime means any number greater than 1, and its only factors are 1 and itself. Some examples of prime numbers are 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 39, 41, and 43. If we go back to the problem 2×4=8, clearly 4 is not a prime number; therefore, we have to break it down until it is a prime number. To break down 4 into prime numbers we can start by finding a multiple of 4, which is 2 (2×2 = 4). Now we have all prime numbers: 2x2x2=8; this is the same as saying 2×4=8.

Factor trees help to find the prime factors of a number by first obtaining any two factors and then obtaining their factors. This may seem confusing, but it is actually quite simple. For example if we have the number 40, we can start by obtaining any two factors (8×5). Since 5 is already a prime number, we only need to obtain the factors of 8. These factors could be 4×2. Once again, 2 is a prime number; therefore we only need to break down the number 4. The number 4 breaks down into 2×2. Now we have all the prime factors of 40: 5x2x2x2=40. I have provided a picture of a factor tree to help visualize the problem.

A fun game that involves practicing factors is called Roast Turkey. This game helps to gain further knowledge of factors and helps to practice them. The game begins by letting the player choose what level you want. After you choose your level, it explains that you use your keyboard arrows and space bar to navigate “Professor Super”. Once you click the begin button, it will bring up a page that explains factors. Now it is time to begin the game; a question will pop up like: what is not a factor of 25. There will be three uncooked turkeys floating around your screen with different numbers in each one. You have to use the arrows to navigate “Professor Super” and the space bar to “fire” the correct turkey. This is a fun interactive factoring game!

Describing Division

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Division can be a tricky, but understanding some basic terms can help. There are three basic terms to describe a division problem; they are dividend, divisor, and quotient. An example of this is 24/6=4. In this example the 24 is the dividend, 6 is the divisor, and 4 is the quotient.

There are two different concepts to find the solution to a division problem. They are the sharing concept and the measurement concept. The sharing concept uses the divisor to divide the problem into number of groups, and uses the quotient to determine how many parts are in each group. A great way to visualize this is by using fruit. For example, we have a total of 24 apples, and we want to divide them equally between 6 groups. How many apples will each group receive? According to the sharing concept the divisor, 6, is used to find the number of groups, and the quotient, 4, is used to find the number of apples in each group. This means we will have 6 groups with 4 apples in each group. On the other hand, the measurement concept uses the quotient to divide the problem into number of groups, and the divisor to determine how many parts are in each group. If we use the apple problem again, there would be 4 groups with 6 apples in each group. The picture provided may help to clear up any confusion about the concepts.

Drawing pictures is a great way to practice division, but I have also found a fun game that is great for practice. The game is called Alien Munchtime; in the game it allows you to choose the fact families that you need help with. The choices include 2 through 12. After you have chosen your fact families, an alien pops up and says she needs help serving lunch. Once you click the “lets go” button the game begins. Hungry alien students come through the lunch line with a division question like 88/8 and you have to serve them the answer like 11. This is a great way to get practice with division and have fun at the same time!