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QuestionWhat’s the formula of the least common multiple?This answer was written by one of our trained team of researchers who validated it for accuracy and comprehensiveness.wikiHow Staff EditorStaff AnswerThe formula is lcm(a, b) = a × b / gcd(a, b), where a and b are the numbers for which you want to find the LCM, and GCD is the greatest common divisor.
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QuestionIs there a least common multiple calculator?This answer was written by one of our trained team of researchers who validated it for accuracy and comprehensiveness.wikiHow Staff EditorStaff AnswerYes, there are multiple LCM calculators online. Try websites like CalculatorSoup.com or Calculator.net to find calculators for finding the LCM and doing a variety of other common calculations.
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QuestionWhat’s the fastest way to find the least common multiple of two numbers?This answer was written by one of our trained team of researchers who validated it for accuracy and comprehensiveness.wikiHow Staff EditorStaff AnswerOne quick and easy way to do it is to start by finding the greatest common factor (GCF) of the 2 numbers. Divide the GCF into either one of the 2 numbers, then multiply the result by the other number. This will give you the LCM.
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QuestionWhat is the least common multiple of 105, 210 and 630?Community AnswerThe least common multiple of 105, 210 and 630 is 630. Both 105 and 210 are factors of 630, therefore 630 is the least common multiple of the three numbers. To verify this, see that 105 x 6 = 630, 210 x 3 = 630, and 630 x 1 = 630.
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QuestionHow do I calculate the least common multiple and lowest common denominator of fractional numbers?Community AnswerTo find the lowest common denominator of a fraction, you need to find the LCM of the two denominators.
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QuestionWhat are the two numbers that have the least common multiple of 20?Community AnswerSince 20 x 1 = 20, 20 is a multiple of 20. That means 10 and 20 are the two numbers that have an LCM of 20.
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QuestionWhat is the lowest common multiple of 16 and 20?Community Answer16 = 2 x 2 x 2 x 2 20 = 2 x 2 x 5 Since both share a factor of 2 twice, begin by writing 2 x 2. 16 two factors of 2 left over, so the multiplication sentence becomes 2 x 2 x 2 x 2 20 has a factor of 5 left over, so the multiplication sentence becomes 2 x 2 x 2 x 2 x 5 = 80. So, the LCM of 16 and 20 is 80.
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QuestionI applied Method 1 to the numbers from Method 4: 210 and 45. I came up with an LCD of 420, which is not right. Where did I go wrong? (210=2x3x5x7, 45=3x3x5) leading to (1x2, 2x3, 1x5, 1x7) leading to 420.OrangejewsCommunity AnswerYou are right that the LCM is 2×3×3×5×7. But that comes out to 630, not 420. Perhaps you accidentally wrote a 2 instead of 3 at some point while multiplying out that last step.
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QuestionWhat is the LCM for (a-n) and (a-n)²?DonaganTop Answerer(a-n)².
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QuestionWhy in the first method is 42 used instead of 2?Community AnswerUsing 2 instead of 42 in the first method would be too easy to solve. Since 2 is a factor of 20, the first multiple that is common to both of them will be 20. This is because if a number n is a factor of a number p, then the LCM of n and p will always be P. Using the number 42 really shows that we commonly have to solve a problem in which two numbers are not relatively prime, but is relatively large as to pose a challenge to us.
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QuestionWhy do I need to take prime factors for the least common multiple?DonaganTop AnswererUsing prime factors is simply a quicker, more efficient or direct way of looking for an LCM, as shown in Method 2 above.
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QuestionIf the LCM of two numbers is given, how do I find those two numbers?V's Online Math TutoringCommunity AnswerJust by knowing the LCM, you cannot find the exact 2 numbers. You'll have a number of options, though. For example, let the LCM of 2 numbers be 20. The numbers can be 1 and 20, 2 and 20, 4 and 20, 5 and 20, 10 and 20, 4 and 5, 4 and 10, etc. If you have additional constraints (e.g. if the 2 numbers have to add to 9 and have an LCM of 20, then the numbers have to be 4 and 5).
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QuestionHow do I find the LCM for 17, 24 and 53? There are 2 prime numbers. I can't factor them.V's Online Math TutoringCommunity AnswerIf you can't find common factors for any of the numbers (other than 1), you just multiply then to get the LCM. LCM of 4 and 5 is 20. 4 and 5 do not have any common factors (other than 1) so 4 * 5 = 20 is their LCM. Similarly, 17, 24 and 53 have no common factors (no common factor for 17 and 24, 17 and 53 or 24 and 53), so their LCM is 17 * 24 * 53 = 21,624.
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QuestionSo if I am doing method three, what if one number is even and one number is odd?DonaganTop AnswererThat just means that they don't share 2 as a factor. They may share some odd number as a factor, however, and you can still use Method 3.
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QuestionWhat's the LCM for 1944 and 324?DonaganTop AnswererThe LCM is 1,944. 1,944 = (6)(324).
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QuestionHow do I find the GCF for a fraction?DonaganTop AnswererBreak the numerator down into its prime factors. Do the same with the denominator. Look at the two groups of prime factors, and find the largest combination of prime factors common to both numerator and denominator. Multiply that group of prime factors together to get the GCF.
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QuestionTo find the least common multiple, should I factorize by only prime numbers?DonaganTop AnswererYes. As shown above, whenever you look for a number's factors, you keep breaking the factors down until you're left with prime numbers only. This makes it easier to identify the least common multiples of two (or more) numbers.
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QuestionThe gcf of 2 different numbers is greater than lcm of the numbers. Always, sometimes, or never?Community AnswerGo with 'never'. A factor can never be greater than (any of) the number(s) it's a factor of, and a multiple can never be less than (any of) the number(s) it's a multiple of. So your ordering will be lcm >= larger number > smaller number >= gcf.
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QuestionHow do I find the LCM of three numbers?Top AnswererFind the LCM of the first two numbers, and then find the LCM of that result and the last number.
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QuestionHow do you find the LCM of 12 and 60 without factorization?Community AnswerIf you notice that 60 is a multiple of 12, it becomes a simple problem: the LCM is 60. If you don't notice that, however, or if that condition does not exist, you'll have to multiply the two numbers together and then reduce the product as much as possible by repeatedly dividing by whatever small prime numbers will divide evenly into the product -- like 3, 5, 7, etc. Reduce until or before you reach the largest of the original numbers (12 and 60 in this case).
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QuestionWhat are the factors of 32?Community Answer1, 2, 4, 8, 16, and 32.
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QuestionWhat if it's a prime number?I_l1ke_gam3sCommunity AnswerIt is the same process. However, if you're trying to find the LCM of two prime numbers, it is the product of the prime numbers.
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