3 Common Mistakes Made when Adding and Subtracting Fractions with Unlike Denominators

  1. When adding and subtracting fractions with unlike denominators, a common mistake many of my students’ make is not renaming the fractions. The first step
    is to rename the fraction using a LCD (lowest common denominator). For example, let us take a look at the
    following problem:

  1. 2. The second mistake that is quite common many of
    my students make when adding and subtracting fraction is adding the numerators
    and denominators. You are only supposed to add the numerators. The denominators
    stay the same:

  1. 3. Another mistake that is also common when adding
    and subtracting fractions is not simplifying the fraction to lowest terms. The
    above example is in lowest terms. The following example is not so we have to
    simplify it:

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Figure This Challenge #56

  • Complete Solution will be given on May 17, 2015

Complete Solution:



Created by Wanda Collins May 10, 2015 at 1:56pm. Last updated by Wanda Collins May 10, 2015.

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Fun Math Facts:

Math Limerick

Question: Why is this a mathematical limerick?

( (12 + 144 + 20 + 3 Sqrt[4]) / 7 ) + 5*11 = 92 + 0 .


A dozen, a gross, and a score,
plus three times the square root of four, divided by seven, plus five times eleven, is nine squared and not a bit more.

---Jon Saxton (math textbook author)

Presentation Suggestions:
Challenge students to invent their own math limerick!

The Math Behind the Fact:
It is fun to mix mathematics with poetry.


Su, Francis E., et al. "Math Limerick." Math Fun Facts.


Pre-K, Kindergarten, First, Second, Third, Fourth, Fifth, Sixth, Seventh, Eighth, Ninth, Tenth, Eleventh, Twelfth, Higher Education, Adult Education, Homeschooler - TeachersPayTeachers.com


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