What is 1/9 of 21?

How to calculate 1/9 of 21?

1. Multiply the whole number by the numerator of the fraction: 21 × 1 = 21
2. Divide this result by denominator of the fraction: 21/9 = 2.3333333333333
3. Simplify by dividing both the numerator and denominator by their GCD (3):
   • 21/3 = 7
   • 9/3 = 3
4. Which gives: 7/3

Since 7/3 is an improper fraction, the result could also be expressed as a mixed number: 2 1/3

How does it work?

The principle behind finding a fraction of a number, such as 1/9 of 21, is rooted in the method of cross-multiplication.

Consider the following proportion: $\frac{1}{9}=\frac{x}{21}$ (where x represents 1/9 of 21)

1. Using the cross-multiplication method, multiply both numerators by their opposite denominators: $1\times 21=9x$
2. Which gives: $21=9x$
3. Divide both sides by 9 to isolate x: $\frac{21}{9}=\frac{9x}{9}$
4. Which gives the result: $\frac{21}{9}=x$ (or $\frac{7}{3}=x$)

Thus, 1/9 of 21 is equal to 7/3 (or 2.3333333333333 in its decimal form).