YouTube Video: Fraction of a Number using multiplication by the fraction This method by northstar15 is in just one step. Two-fifths of 80 is calculated by multiplying two-fifths and 80. The one step process is better when explaining the calculation in an exam. Less writing is needed than the two step method.
This video writes the calculation using a horizontal dividing line to separate numerator and denominator, as in: $${{2 \over 5} \times {{80} \over 1}}$$ The 1 in the $${{80} \over 1}$$ is not necessary and so the calculation can be written more simply as: $${2 \over{5}}$$ × 80 = $${2 \over\bcancel{5}_1}$$ × $${\bcancel{80}_{16}}$$ = 2 × 16 = 32 The same calculation 2⁄5 of 80 can be written or typed as 2⁄5 × 80 and simplifies to: 2⁄5 × 80 = 2⁄$${\bcancel{5}_1}$$ × $${\bcancel{80}_{16}}$$ = 2 × 16 = 32
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