![]() So if we multiply the denominator by five, we have to multiply the So what did we do go from six to 30? We had to multiply by five. So 1/6 is what over 30? I encourage you to pause the video and try to think about it. I can also write 1/6 with a denominator of 30. With a denominator of 30, and that's useful because So once again, 9/10 and 27/30 represent the same number. The numerator by three and the denominator by three,Īnd that doesn't change the value of the fraction. I have to multiply that by three as well because now I'm just multiplying The value of the fraction, I have to do the same How would I write that as something over 30? Well I multiply the denominator, I'm multiplying So I could rewrite both of these fractions as something over 30. The smallest multiple of 10 that is divisible by six?"Īnd that's going to be 30. The multiples of 10 and saying, "Well what is Is start with the larger denominator here, 10, and say, So what's a common multiple of 10 and six? And it's usually simplest toįind the least common multiple, and a good way of doing that Gonna have to be a common multiple of these twoĭenominators of 10 and six. So how do you think aboutĪ common denominator? Well, a common denominator's It's not obvious how I add these." And you'd be right and the way to actually move forward is to findĪ common denominator, to convert both of these fractions into fractions that have a common denominator. What is this, what is this going to equal? So when you first look at this, you say, "Oh, I have different denominators here. We have the fraction 9/10, and I want to add to These values 4 and 7 become 4/4 and 7/7 because we have to multiply each fraction by a value = 1 to have an equivalent fraction. What times 4 will create a denominator of 28? The answer is 7. You do the same thing to determine how to convert 3/4 to have a denominator of 28. To convert the fraction 1/7 to have a denominator of 28, you ask yourself the question: what times 7 will create 28? The answer is 4. So, we start by find the lowest common multiple(LCM), also called the lowest common denominator (LCD) of the fractions. Since the fractions in the video don't have a common denominator, they need to be converted to have a common denominator. Now to your questions - Where did the 4/4 and 7/7 come from? We're just converting it to an equivalent value. So, by multiplying a fraction by 4/4 = 1, we aren't changing the value of the fraction. Why? This is based upon the identity property of multiplication: Any number times 1 = the original number. This is called a "common denominator".ģ) Equivalent fractions are created by multiplying both numerator & denominator by the same value. So, we have to force the denominators to have a common value. If a pizza is cut int 4 slices, then each slice is 1/4 of the pizza and a slice is twice as big as a slice of 1/8Ģ) To add & subtract fractions we need to work with fractions of the same size. ![]() Visualize a pizze that was cut into 8 slice. I thought I worked out how they did it but my brain refused to accept what it thought was either a convoluted approach or that I was creating my own incorrect method lolĬan anyone provide a possible clarification of why they would suggest using this method rather than the easy cross multiplication method?ġ) The denominator of a fraction tells you the size of each portion. I have no idea how they got the 4/4 and 7/7 try as I might and how the strange-looking order of the terms after the equal sign even if I overlooked how they got those numbers to begin with. ![]() To get identical bottom numbers, we begin by multiplying each number by 1, written as quarters in one case, and as sevenths in the other." "Here, we can neither convert sevenths to quarters nor quarters to sevenths, so we’re going to learn a method that you can use to add or subtract any fractions. The book I am reading has stumped me in the addition of fractions. I just don't want to ignore it just in case there are situations where it needs to be used which I find is always the case that there are rules that work for some combination of things and not others. I am reading a book and it does not seem clear to me how or why it works or why you would use it at all rather than the easy cross multiplication method. Does anyone know why when adding 2 fractions you would multiply each fraction by 1?
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