Q&A for How to Subtract Fractions

Take the LCM of denominator of both the fractions (the denominator of whole number is one). Then, in both the numbers divide the LCM by the denominator and multiply the result by the numerator. Subtract the numbers in numerators and you will get your answer.

1/4 - 5/6 = -7/12. That is a negative number.

Turn them into improper fractions. Then you can make the denominator the same to subtract them. Don't forget to simplify if necessary.

In order to simplify a fraction, find a number that both the numerator and the denominator are divisible by. For example, say your have to simplify 81/9. Both 81 and 9 are divisible by 9. Therefore, it should look something like this: 81/9= 9/1=9. Or, another one: 15/45= 1/3.

The two denominators must be made the same. Multiply the two denominators together: 4 x 3 = 12. Let 12 be the new denominator in both fractions. Change each numerator so that the values of the two fractions remain the same as they were. Change the numerators by dividing their respective denominators into the new denominator and then multiplying the resulting number by the original numerators. For the fraction 3/4, 12÷4=3, and 3x3=9. So 9 is the new numerator and 12 is the new denominator. For the fraction 1/3, 12÷3=4, and 4x1=4. So 4 is the new numerator and 12 is the new denominator. So now you're subtracting 4/12 from 9/12, which is 5/12.

There are two ways to go about doing this. I'll show you the easy one. The first one is the easy way, just multiply the numerator and denominator of one of the fraction's by the other fraction's denominator and vice versa. Then subtract the numerators and put that over the new denominator. You may need to simplify. Here's the example: 3 1 - + - 4 3 3 3*3 9 - => ------ => -- 4 4*3 12 1 1*4 4 - => ------ => -- 3 3*4 12 9 4 11 -- + -- => -- 12 12 12 If you were looking for the second numerator of this problem, since there are three (9, 4, and 11), you choose.

Turn the whole number into a fraction with the same denominator as the fraction that is being subtracted. Then, subtract & simplify. Or, "borrow" 1 from the whole #, and turn that into a fraction with the same denominator as the fraction you are subtracting. Then subtract the fractions, and don't forget to bring down the (whole #-1) for the answer. Example: 3-3/4= 3/1-3/4. Make denominators the same to get 12/4-3/4= 9/4. Simplify to 2 1/4.

-5/2 - 3 = -5/2 - 6/2 = -11/2 = -5½.

Multiply the first fraction by the denominator of the second and multiply the second fraction by the denominator of the first. For example, 3/5 + 2/4 [3/5·4 (12/25) + 2/4·5 (10/25)] = 12/25 + 10/25 = 22/25. You may need to simplify.

You can find an equivalent fraction by multiplying both the numerator and denominator by the same number. For example, multiplying both terms of 3/5 by 2 results in the equivalent fraction 6/10. Multiplying by 10 results in the equivalent fraction 30/50.

Let's assume you're subtracting a smaller fraction from a larger fraction (or even just a smaller number from a larger number). (If that's not the case, fraction strips don't work as well.) Start with a strip (or bar) representing the larger number. Place another strip representing the smaller number on top of the first strip so that the left (or right) end of the top strip lines up exactly with the left (or right) end of the bottom strip. Then measure what amount of the first strip is not being covered by the second strip. The uncovered amount is the difference between the strips and the difference between the fractions. The uncovered amount is the answer you're looking for.

Change 5 3/8 to 43/8. Change 3 3/4 to 3 6/8, then to 30/8. 43/8 - 30/8 = 13/8 = 1 5/8.

First reduce: 32/34 = 16/17, and 6/16 = 3/8. Convert both fractions to equivalent fractions having the same denominator. Do that by multiplying the denominators together: 17 x 8 = 136. Then convert 16/17 to an equivalent fraction by dividing 17 into 136 (that's 8) and multiplying 8 by 16, which is 128, the new numerator. So 16/17 = 128/136. For the other fraction, 3/8, convert it to an equivalent fraction by dividing 8 into 136 (that's 17) and multiplying 17 by 3, which is 51, the new numerator. So 3/8 = 51/136. Now you can subtract 51/136 from 128/136, which is 77/136, your answer (which doesn't reduce).

16 4/20 is equal to 15 24/20. From that subtract 14/20, which equals 15 10/20, or 15½.

First, we need to make the fractions top heavy. The denominators will both be 8 as this will make subtracting easy. For the numerator, we must multiply the integer we have by the denominator and add it to the current numerator. 10 1/8 = 81/8 and 5 5/8 = 45/8. Now we have to subtract the fractions, 81/8 - 45/8 = 36/8. To complete, we must make sure the fraction isn't a top heavy, 36/8 = 4 6/8 = 4 3/4.

31¾ - 12½ = 31¾ - 12 2/4 = (127/4) - (50/4) = 77/4 = 19¼.

21/2 - 6/4 = 21/2 - 3/2 = 18/2 = 9.

Subtracting a negative fraction is the same as adding a positive fraction. For instance, 3/4 - (- 1/2) = 3/4 + 1/2 = 3/4 + 2/4 = 5/4 = 1 1/4.

First convert the mixed numbers to improper fractions: 17/2 = 12/5 + m. Next convert the improper fractions to equivalent fractions that share the same denominator: 85/10 = 24/10 + m. Now subtract 24/10 from both sides: 61/10 = m. m = 6 1/10.

First convert each mixed number to an improper fraction: 141 3/5 = 708/5, and 2 3/5 = 13/5. Now multiply the two improper fractions together: (708/5)(13/5) = 9204/25. You can leave the answer in that form or convert it to a mixed number: 368 4/25.

2 + 1 = 3. 1/2 + 1/2 = 1. 3 + 1 = 4. 4 + 2/3 = 4 2/3.

Since the denominators are the same, just subtract the second numerator from the first, and keep the denominator the same. Reduce the answer if necessary. 9/15 - 12/15 = -3/15 = -1/5.

First convert each mixed number to an improper fraction: 11/4 + 17/5 - 5/3. Now find the lowest common denominator: it's 60. So now the expression becomes 165/60 + 204/60 - 100/60 = 269/60 = 4 29/60.

(4.2 / 9) + (1.5 / 5) - (2.1 / 3) = (0.47) + (0.30) - (0.70) = 0.07.

It is certainly possible, but in some cases it gets tricky. It's a more reliable method to convert to improper fractions first. That's why they teach that method in school.

Subtract fractions as shown above. As for reducing fractions, see Reduce Fractions .

Factoring isn't involved here. 3/50 - 1/35 = 21/350 - 10/350 = 11/350. (The only challenge here is finding the lowest common denominator. It's not too hard if you recognize that there is a multiple of 35 (350) that is also a multiple of 50.)

8/9 - 5/6 = 16/18 - 15/18 = 1/18. (The only challenge here is finding the lowest common denominator. If you don't recognize that 18 is a multiple of both 9 and 6, you would have to multiply 9 by 6 and use 54 as the common denominator and then reduce the fraction at the end.)

When you subtract a larger number from a smaller number, the result is a negative number. For example, 2/5 - 3/5 = -1/5.

3 2/5 - 5 4/5 = 17/5 - 29/5 = -12/5 = -2 2/5.