How can i find the lowest common denominator

We also have calculators for least common multiple , math with fractions , simplifying fractions , math with mixed numbers , and comparing fractions.

Basic Calculator. Find the LCD of: enter values separated by commas. To find the lowest common denominator, we see if the larger denominator 20 can be divided by the smaller denominator 4. We then need to work out what we need to multiply the 4 by, to make 20 this is 5.

Another example is these fractions: The larger denominator 9 is a multiple of the smaller denominator 3. More like this. What is the denominator? Adding and subtracting fractions with the same denominator.

Rewrite the original equation. In order to change each fraction in the equation so that it remains true to the original equation, you will need to multiply each numerator the top of the fraction and denominator by the same factor used to multiply the corresponding denominator when reaching the LCD.

Solve the rewritten problem. After finding the LCD and changing the fractions accordingly, you should be able to solve the problem without further difficulty. Remember to simplify the fraction at the end. Method 2. List all of the factors of each denominator. The factors of a number are all of the whole numbers that are evenly divisible into that number.

Every number has a factor of 1, because every number can be evenly divided by 1. Factors of 8: 1, 2, 4, and 8 Factors of 1, 2, 3, 4, 6, Identify the greatest common factor between both denominators. Once you have listed the factors of each denominator, circle all of the common factors. The largest of the common factors is the greatest common factor GCF that will be used to continue solving the problem.

In our example, 8 and 12 share the factors 1, 2, and 4. The greatest common factor is 4. Multiply the denominators together. In order to use the greatest common factor to solve the problem, you must first multiply the two denominators together.

Divide this product by the GCF. After finding the product of the two denominators, divide that product by the GCF you found previously. This number will be your least common denominator LCD. Divide the LCD by the original denominator. To determine the multiple needed to make the denominators equal, divide the LCD you determined by the original denominator. Multiply the numerator and the denominator of each fraction by this number.

The denominators should now both be equal to the LCD. Solve the rewritten equation. With the LCD found, you should be able to add and subtract the fractions in the equation without further difficulty. Remember to simplify the fraction at the end, if possible. Method 3.

Break each denominator into prime numbers. Factor each denominator digit into a series of prime numbers that multiply together to make that number. Prime numbers are numbers that cannot be divided by any other number. Count the number of times each prime appears in each factorization. Tally up the number of times that each prime number appears in the factorization of each denominator digit. Take the largest count for each prime. Identify the largest number of times you used each prime number for any of the denominators and note that count.

So we factor each number into primes. When we do our largest count of the prime numbers, we find three 2s , and two 3s do you see them? Now we have our least common denominator of Next… we convert each fraction to an equivalent fraction using 72 as our new denominator.

Mission accomplished… all of our denominators are the same , so we can just add up the numerators. Now adding all of the numerators and placing the results over our common denominator , the answer is…. Since our answer is an improper fraction the numerator is larger than the denominator , we now have three options.