What is 5/6 of 21?

How to calculate 5/6 of 21?

1. Multiply the whole number by the numerator of the fraction: 21 × 5 = 105
2. Divide this result by denominator of the fraction: 105/6 = 17.5
3. Simplify by dividing both the numerator and denominator by their GCD (3):
   • 105/3 = 35
   • 6/3 = 2
4. Which gives: 35/2

Since 35/2 is an improper fraction, the result could also be expressed as a mixed number: 17 1/2

How does it work?

The principle behind finding a fraction of a number, such as 5/6 of 21, is rooted in the method of cross-multiplication.

Consider the following proportion: $\frac{5}{6}=\frac{x}{21}$ (where x represents 5/6 of 21)

1. Using the cross-multiplication method, multiply both numerators by their opposite denominators: $5\times 21=6x$
2. Which gives: $105=6x$
3. Divide both sides by 6 to isolate x: $\frac{105}{6}=\frac{6x}{6}$
4. Which gives the result: $\frac{105}{6}=x$ (or $\frac{35}{2}=x$)

Thus, 5/6 of 21 is equal to 35/2 (or 17.5 in its decimal form).