To subtract one fraction from another, like 2/3 – 1/4, model the minuend 2/3 using a 2-unit rod over a 3-unit rod and the subtrahend 1/4 using a 1-unit rod over a 4-unit rod. To find a common denominator, create a train of 3-unit rods and a train of 4-unit rods until both are the same length. Both trains have the same length when they are 12 units long, so 12 is a common denominator. The fractions 2/3 and 1/4 can be expressed as equivalent fractions 8/12 and 3/12. Because the denominator represents the number of equal parts in a whole and the numerator represents the parts in the quantity, subtract the numerator 3 from the numerator 8. There are 5 parts remaining, so 2/3 - 1/4 equals 5/12.

Subtracting Fractions using the Brainingcamp Cuisenaire® Rods virtual manipulative.

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