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HESI A2 · Mathematics · 6 min read

Fractions and Mixed Numbers

In this lesson you will
  • Identify, classify, and simplify proper fractions, improper fractions, and mixed numbers.
  • Compare fractions using common denominators, cross-multiplication, and decimal conversion.
  • Perform addition, subtraction, multiplication, and division with fractions and mixed numbers, expressing all results in lowest terms.

Fraction Anatomy and Classifications

A fraction represents division and describes part of a whole. In mathematical notation, a fraction is written as a numerator positioned over a nonzero denominator. The numerator, which is the top number of the fraction, indicates the specific number of equal parts being considered. In contrast, the denominator, located at the bottom of the fraction, indicates the total number of equal parts that make up the entire whole. When considering an everyday object divided into equal segments, the denominator reflects the complete group of segments, while the numerator accounts for the segments selected. It is essential to remember that a fraction with a denominator of zero is mathematically undefined.

Fractions are classified based on the relationship between their components. For nonnegative fractions written with a positive denominator, a proper fraction has a numerator smaller than its denominator and a value less than 1. For nonnegative fractions written with a positive denominator, an improper fraction has a numerator greater than or equal to its denominator and a value of at least 1. A mixed number presents another way to express these quantities; it consists of a non-zero whole number positioned alongside a proper fraction.

A positive improper fraction can be written as a mixed number if it has a nonzero remainder when divided; otherwise, it simplifies to a whole number. To convert a positive mixed number into an improper fraction, multiply the whole number by the denominator, add the numerator to this product, and place the resulting value over the original denominator. Divide the numerator by the denominator; if the remainder is nonzero, write the quotient alongside the remainder over the original denominator, and if the remainder is zero, write the quotient as a whole number.

Classifications of Fractional Forms
Fraction FormDefining Structural RelationshipRelationship to the Whole
Proper FractionNumerator is strictly less than the denominatorRepresents a value less than one whole
Improper FractionNumerator is greater than or equal to the denominatorRepresents a value equal to or greater than one whole
Mixed NumberNon-zero whole number alongside a proper fractionRepresents a combined whole and fractional value

Common mistakes

  • Adding or subtracting denominators when combining like or unlike fractions instead of maintaining the common denominator.
  • Attempting to add or subtract fractions with unlike denominators before converting them to share a common denominator.
  • Inverting the dividend rather than the divisor when executing fraction division.
  • Forgetting to add the value of the denominator to the numerator when borrowing 1 from the whole number during mixed-number subtraction.

Key points

  • A fraction represents division and describes part of a whole with a numerator over a nonzero denominator, whereas a denominator of zero is undefined.
  • For nonnegative fractions written with positive denominators, a proper fraction has a numerator smaller than its denominator, an improper fraction has a numerator at least as large as its denominator, and a mixed number combines a nonzero whole number with a proper fraction.
  • A fraction is in simplest form when the greatest common factor of its numerator and denominator is 1, and final answers should be written in lowest terms.
  • Fractions with unlike denominators require a common denominator before addition or subtraction, but denominators are never added or subtracted.
  • Multiplying fractions involves multiplying numerators together and denominators together without finding a common denominator, and cross-canceling simplifies calculations.
  • Dividing by a nonzero fraction is executed by multiplying the dividend by the reciprocal of the divisor, and zero has no reciprocal.

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Original lesson written for HESI A2 practice · updated October 30, 2026. Exam names are trademarks of their owners; tests.global is not affiliated with them.