What is 4/9 of 81?

How to calculate 4/9 of 81?

1. Multiply the whole number by the numerator of the fraction: 81 × 4 = 324
2. Divide this result by denominator of the fraction: 324/9 = 36
3. Simplify by dividing both the numerator and denominator by their GCD (9):
   • 324/9 = 36
   • 9/9 = 1
4. Which gives: 36/1

How does it work?

The principle behind finding a fraction of a number, such as 4/9 of 81, is rooted in the method of cross-multiplication.

Consider the following proportion: $\frac{4}{9}=\frac{x}{81}$ (where x represents 4/9 of 81)

1. Using the cross-multiplication method, multiply both numerators by their opposite denominators: $4\times 81=9x$
2. Which gives: $324=9x$
3. Divide both sides by 9 to isolate x: $\frac{324}{9}=\frac{9x}{9}$
4. Which gives the result: $\frac{324}{9}=x$ (or $\frac{36}{1}=x$)

Thus, 4/9 of 81 is equal to 36/1 (or 36 in its decimal form).