# How To Subtract Dissimilar Fractions?

## 4 Answers

Connor Sephton answered
There are two parts to every fraction. The top part is the numerator and the bottom part is the denominator. In order to subtract a fraction, you must first make sure that the denominators are the same number. You cannot subtract two fractions that have different denominators. For example, you cannot subtract 1/6 from ½ in its original form. In order to make the bottom numbers the same, multiply the top and bottom of the first fraction (1/2) by 3. You want to multiply the numbers that will result in the denominator being equal to the other fraction's denominator. This is because to get the denominator to be 6, you need to multiply 2 by 3. The resulting problem is 3/6 - 1/6. The numerator will change when this is done, but it is still equal to the original fraction. For example, 3/6 is equivalent to ½.

The next step is to subtract the numerators. You must put the answer over the same denominator. For example, 3 - 1 = 2 would be the answer for the numerator. The denominator remains the same. The answer would be 2/6. The answer needs to be simplified in order to be accurate. To simplify the fraction, you need to find the largest number you can divide both sides by evenly.  In this case, it would be two. Two divides into two once, and two divides into six three times. The result is 2/6=1/3 when simplified. Prime numbers are not divisible by any number, and therefore are considered to be simplified numbers. One and three are prime numbers, and this is why 1/3 is a fully simplified fractions. Simplified fractions are easier to read, and easier to use in other problems. The ending result is ½-1/6= 1/3. This format can be applied to most dissimilar fractions.
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Anonymous answered
Get the LCD of the denominators and then divide the LCD to the 1st denominator then multiply it to the numerator and do the same to the next fraction! :D
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Oddman answered
1. Rewrite them as similar fractions. 2. Subtract in the usual way for similar fractions.
You can also use the formula   a/b - c/d = (ad - bc)/(bd)  If e is the largest common factor of b and d, then you may be able to avoid having to reduce the answer by calculating it as   (ad/e - bc/e)/(bd/e)  Example   3/4 - 7/10 = ?   By the first formula: (3*10 - 4*7)/(4*10) = (30 - 28)/40 = 2/40, which reduces to 1/20   By the second formula: (3*10/2 - 4*7/2)/(4*10/2) = (15 - 14)/20 = 1/20    (we note that 2 is the greatest common factor of 4 and 10). This formula essentially rewrites the problem as   15/20 - 14/20 = 1/20, which is what the steps 1 and 2 are telling you to do.
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Oddman answered
Given   2/3 - 1/4 Find   The result in lowest terms. Solution   Find a common denominator. This will be the least common multiple of the denominators.   LCM[3, 4] = 3*4 = 12   2/3 = (2/3)*(4/4) = 8/12   1/4 = (1/4)*(3/3) = 3/12   The difference is   8/12 - 3/12 = 5/12   5 and 12 have no common factors, so the result in lowest terms is   2/3 - 1/4 = 5/12.
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