Monday, October 18, 2010

Tutorial: Subtracting Across a Zero

Today we reviewed how to subtract 3-digit and 4-digit numbers. Normally, we just borrow from the place value position to the left. However, today there was a zero and we couldn't borrow!

Here is a video showing one strategy for subtracting when the neighbor is a zero.

How did it work for you?

Did you find any problems where there were TWO zeros?
What did you do? 


  1. Dear Mrs Yollis and students,

    Thankyou for this wonderful posts.
    I really liked this concept of subtracting across a zero.

    Also I liked how you showed each step you need to come to the correct answer.
    I will have to use this method when I subtract as to tell you the truth I much rather add than subtract.

    Well done from your blogging buddy from down under AA.

  2. Dear Mrs. Yollis,

    I ♥ ed your video! I noticed many things you did well. I think subtracting with 0's is pretty tricky!
    I tried some extra math problems at home so I can know it like it is my name. I also think subtracting is much harder than adding. Your way is easy, simple, and it works! I will try really hard practicing.

    I have some questions for you.
    Did it take a long time to make the video?
    Do you know any other ways to subtract?


  3. Dear Nick,

    I loved your video! You spoke loudly and clearly. You were able to explain subtracting across a zero in a way that made it easy to understand.

    I have a question for you. Were you nervous when you were making the video?

    Your friend,

  4. Dear Nick,

    I really liked your video about the subtraction problem. I have some questions.

    1.Was the problem easy?

    2.Do you know a trick to subtract?


  5. Dear Mrs. Yollis,

    My brother Ethan and I watched your video. We really liked it. Your method makes things very easy.

    We are here in Boston with my uncle and his family. They just had a new baby.

    My family will be returning to L.A. soon. We can't wait to see our friends. It has been a fun trip.

    Today we went to the Museum of Science. We learned about dinosaurs and engines. They had a space machine that took us on a trip to international space station.

    See you soon,

  6. Dear Nick
    Your use of Mrs Yollis' strategy was clear and easy to follow. It was good to see a second example of the strategy, as now I will remember it more easily.

    The children in B4 are not working on renaming tens yet, so I will have to store this strategy away for now.

    At the moment some children in B4 are learning to add 2 digit numbers by counting on in tens.

    What is your favourite part of maths?
    from Mrs McKenzie

  7. Dear Nick,

    What an outstanding video! I liked how you spoke loudly and VERY clearly. Was it hard to do the video? Were you a little scared? Was it fun?

    See you later,


  8. @ Kristen,

    I liked your comment very much. The problem was a little easy, but subtracting 0's was kind of hard. A faster way to subtracted is to cross out numbers and add 10,11,12,and other numbers.


  9. @ Hanna,
    Thank you for the wonderful comment. I was a little nervous in the video, but I got use to it. The problem was hard, then it became less hard.


  10. @ Mrs.McKenzie,

    Thank you for the wonderful comment. My favorite part of math is squaring and crossing off numbers.


  11. @ Adia,
    Making the video was kind of hard.I was a little scared at first,but I got used to it,and it turned out to be lots of fun.Thanks for your wonderful comment.


  12. Dear Mrs.Yollis,
    I know that subtracting by zeros is hard but you show the easy way to do it. My brother loves to subtract across zeros. And I think squaring off is really easy to do math.

    Nick's sister "Sofi"

  13. Dear Mrs. Yollis,

    I'm very glad Nicolas had the oportunity to do the substraction tutorial, we loved the video!
    It was a wonderful learning experience for him.

    Thank you,

  14. Dear Mrs Yollis

    I have just called in and watched your video on subtraction. Very interesting. I hadn't ever thought of the idea of squaring off. Rather than borrowing we call it renaming, which fits beautifully with what you have shown.

    I actually don't teach the written algorithm. We tend to hold back on it as we work on the students solving many problems mentally first. Those that can be solved mentally. Now I am tempted to introduce it a little earlier to some of my students. You have explained it so well.

    Do you also have problems that you encourage students to solve mentally?

    I have been thinking of making some videos for our parents on how we solve problems mentally, as of course they didn't learn such ways. Your video inspires me to get going on it. Thank you!

    Your blogging colleague
    Miss Trask

  15. I loved you movie I like the panda. You gave me lot's of good ideas. we are also leaning about commenting to. we would like to know how to make a movie. sincerely caitlin.

  16. Good Evening, Mrs. Yollis!

    My name is Caitlin, and I am a student of Dr.Strange's EDM310 class at the University of South Alabama.
    What a creative way to show your students how to get around a math problem! I sure wish this technology had been around when I was that age. I had the hardest time with problems that had more than one zero. Whether it's reminding your students how to work out a problem as such, or teaching them how to do it, your video was very helpful and easy to understand. Thank you for sharing it. I'll keep this in mind for one day when I am a teacher.

    Have a great day!

  17. What a great video and method! I have been struggling with teaching this concept to my Title I and Special Ed. students for some time now. This method really "clicked" with them.

    Great job with the student example as well!

    Mr. T
    Indianapolis, IN

  18. I am homeschooling my daughter (3rd grade). I know how to "subtract across zero", but could not explain it in a way that my daughter understood. I "googled" "4 digit subtraction" & found your video. She caught on immediately, as soon as she watched it. Thank you. I will be visiting your website often.

    1. Wonderful! So glad we could help!

      Mrs. Y♥llis

  19. Dear, Mrs. Yollis,

    Thanks so much for this video!!! Even though I have graduated college and know how to add subtract and everything, I don't really like math too much. However, I love mind puzzles. The puzzle I am working on at the moment is a word division puzzle. Instead of numbers they are letters and you have to figure out what number each letter is, which is kinda tricky. Anyway, in one of the problems I got the right solution, but couldn't figure out how they got that answer. I was subtracting 70423 from 64526 and couldn't figure out why there wasn't a 1 in front. I completely forgot about the squaring off, though I remembered the 0 became a 9. This video helped immensely, esp., since I tend to obsess over things when I can't remember something about it, like a name of song or lyrics to a song. Thanks a million!!! :)

    Laura W.


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