How to Calculate a Fraction of a Whole Number

The Organic Chemistry Tutor

This educational video provides a clear, step-by-step tutorial on how to calculate a fraction of a whole number. The narrator demonstrates two distinct methods for solving these problems: the first involves turning the whole number into an improper fraction over one, multiplying the numerators and denominators across, and then dividing the final result; the second, more efficient method involves simplifying or 'cross-canceling' common factors before multiplying to keep the numbers smaller and more manageable. The video covers four specific examples ranging in difficulty. It begins with basic problems like 3/4 of 8 and 3/5 of 20 to introduce the core algorithm. It then introduces the concept of simplification by breaking numbers down into their factors (e.g., rewriting 20 as 5 x 4) to demonstrate how denominators can cancel out factors in the whole number. The final section provides two practice problems (2/3 of 12 and 5/7 of 28) for viewers to attempt on their own. For educators, this video serves as an excellent instructional tool for 4th through 6th-grade math classes. It directly addresses standards regarding multiplying fractions by whole numbers. Teachers can use it to transition students from visual models of fractions to the standard algorithmic procedure. The inclusion of the 'simplifying before multiplying' strategy is particularly valuable for building number sense and algebraic thinking, preventing students from working with unnecessarily large numbers.