The easy way always works, and you should use this method for most of your fraction subtracting needs. The quick trick is a great timesaver, so use it when you can. And
as for the traditional way — well, your teacher and other math purists probably prefer you to use it this way. Cross-multiply the two fractions and subtract the second number from the first to get the numerator of the answer. For example, suppose you want to subtract 6/7 –
2/5. To get the numerator, cross-multiply the two fractions and then subtract the second number from the first number: (6 5) – (2 7) = 30 – 14 = 16 After you cross-multiply, be sure to subtract in the correct order. (The first number is the numerator of the first fraction times the denominator of the second.) Multiply the two denominators together to get the denominator of the answer. 7 5 = 35 Putting the numerator over the denominator gives you your answer. This example puts all the steps together: With the problem set up like this, you just have to simplify the result: In this case, you can reduce the fraction: Subtract fractions with the quick trick methodThe easy way works best when the numerators and denominators are small. When they’re larger, you may be able to take a shortcut.Before you subtract fractions with different denominators, check the denominators to see whether one is a multiple of the other. If it is, you can use the quick trick:
Subtract fractions with the traditional methodYou should use the traditional way only as a last resort, when the numerator and denominator are too large to use the easy way and when you can’t use the quick trick.To use the traditional way to subtract fractions with two different denominators, follow these steps:
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What is the rule for subtracting fractions with unlike denominators?To do this, you need to find the least common multiple (LCM) of the two denominators. To subtract fractions with unlike denominators, rename the fractions with a common denominator. Then subtract and simplify. The LCM of 3 and 11 is 33 .
How do you add and subtract fractions with the unlike denominator?Adding and Subtracting Fractions with Unlike Denominators. STEP ONE: Get a common denominator.. STEP TWO: Add or subtract the numerators.. STEP THREE: Simplify the result if needed. Notice that 3/27 can be simplified, since the numerator and denominator are both divisible by 3.. And that's all there is to it! Final Answer:. |