Today during my office hours, several students asked how to subtract the fraction on the right. My immediate reply, "Oh, you just use criss-cross applesauce," and I proceeded to teach them about how to use criss-cross applesauce to subtract fractions. I told them about how it's a neat trick my high school algebra teacher taught me that I still use to this day. While I thought that many people knew this trick, it seems that not even the Internet has heard of it - at least in the math sense. So, I'm going to fix that. Here is the best way to add and subtract fractions with non-matching denominators. Enjoy!
Yes, I am a nerd.
3 comments:
Very nice, very nice. It kinda seems like that should be intuitive, at least for someone who does math frequently, but very nice pneumonic. Now I'll remember that if I decide to take the GRE sometime.
Criss cross applesauce at my school means that you sit 'indian' style. 'Indian' style's no long PC I guess so they came up with something else. I was boring and called what you described as criss cross applesauce as cross multiplying... so boring.
Thank you for this post. I explained this to my 6th grade daughter who was absent when her class learned it. It seems to be easy enough.
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