Adding and Subtracting Fractions

When two sets of fractions have the same bottom number, or denominator, adding and subtracting them is easy. You just need to add or subtract the top numbers, or numerators, and leave the denominator the same.

However, when the denominators are different you can’t add or subtract the fractions until the denominator is the same. The first thing you need to do in this situation is to change one of the fractions to match the denominator of the other fraction. In the example below that denominator is 6. When you change a fractions denominator, make sure you change the numerator the same amount you change the denominator. In the example below, you multiply both the numerator and the denominator by 2.

How would you solve this?:


You can’t increase the fourths into fifths since 5 can’t be evenly divided by 4, as 6 was by 3 above. In this situation you have to increase the numerators and denominators of both fractions. To find a denominator that can be divided by both 5 and 4, simply multiply 5 by 4 and get 20.

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  • bravo

    i am takinf the ged test and have passed everything except the math on fractions and this part of the adding and subtractions are still confusing to me i guess i need to have it taught to me in elementary teaching i can not comprehend the way it is here

  • Michael

    Thanks for the help.The way you explain it is easy to learn to me.

  • aryonna

    I dont get fractions at all..ughhh i just need math to pass and ill be done wit my ged

  • victoria

    can you please tell me how to solve this this fraction problem
    tessy grew 2 3/8 (2whole number and 3over 8)inches the first half of the year and 1 1/2 (1 whole number and 1over 2) inches the second half of the year how much did he grow during the year?

    • Anonymous

      The answer is 3 7/8

  • KAT

    I am 30 years old and still do not have my GED. The only part i can pass is reading. I feel like I will never pass. Its kind of hard for me but I need to go to collage to support my kids.I want to go to the classes but i don’t have the gas money.I will have to take it online. Has anyone done that? Is it harder that way??

  • Luke

    3 and 7/8

  • CatreshaP.

    Luv,n the site :0) ! # great for begginners &us forgetful ones out here# I also extremely recommend the site for those who are easily distracted by classroom nonsense! Please people curb the distractions we want & need to pass this test!

  • Catresha

    Did,nt get the part about the 11/20 ?? Maybe I missed something??

  • Catresha

    Seen where the 11 came from :0) ! This is a prime example of why we have to pay attention !

  • Felicia


    1/2 of the class has blond hair. 1/4 of the class has black hair. 1/4 of the class has brown hair. If there are 32 kids in the class, how many kids have each color hair?

    How do I solve this? How do you turn a fraction into a normal number?

  • Felicia


    On the first day, Claude read half the book. On the second day, he
    10. read three eighths more, and 40 pages remained. How many pages
    10. were there in the book?

    Ignore that last question I realize that’s easy. lol How would I go about solving this one?

  • CatreshaP.

    Hey Ziyi 🙂 got two problems I need you to help me solve?? 1/2+3/4 and the other is 12 1/2 – 53/8 ?? Please help we need assistance out here asap??!! Thanks ,we appreciate it.

    • CatreshaP.

      I think I got it 1 1/4 is the answer for the first one. The answer for the second one is 53 7/8 :0) please tell me I,m right!!

  • JAX

    The 11 and 20 came from: you multiply 4 times 5 = 20. In the fraction 4 over 5, you multiply by 4 and on the fraction 1 over 4 you multiply by 5 (remember you first multiply 4 times 5. That’s why you are now multiplying by those #) Hope it was helpful!!!

  • Jeannie

    I am taking the GED test on the 6th of next month. I am home schooled and really smart, I just can’t comprehend math. This website has helped me alot! I am actually taking notes on all of it right now. I hope this site helps everybody as much as it has helped me. I used to freak out a little bit any time I would see a fraction, now it is a breeze! Good Luck you guys!

  • laura

    I am 53 and want to get ged. But the math fractions I do not remember. I am not stupid just need someone to explain it to me please. All my kids got there’s. And in college. Thank you.

  • winter gaston

    Thank u I have to do work for my mom and this sight have helped me understand math even more.

  • winter gaston

    Opps I meant *site* lol

  • Lil Wayne


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