What is 7/8 of 90?

How to calculate 7/8 of 90?

1. Multiply the whole number by the numerator of the fraction: 90 × 7 = 630
2. Divide this result by denominator of the fraction: 630/8 = 78.75
3. Simplify by dividing both the numerator and denominator by their GCD (2):
   • 630/2 = 315
   • 8/2 = 4
4. Which gives: 315/4

Since 315/4 is an improper fraction, the result could also be expressed as a mixed number: 78 3/4

How does it work?

The principle behind finding a fraction of a number, such as 7/8 of 90, is rooted in the method of cross-multiplication.

Consider the following proportion: $\frac{7}{8}=\frac{x}{90}$ (where x represents 7/8 of 90)

1. Using the cross-multiplication method, multiply both numerators by their opposite denominators: $7\times 90=8x$
2. Which gives: $630=8x$
3. Divide both sides by 8 to isolate x: $\frac{630}{8}=\frac{8x}{8}$
4. Which gives the result: $\frac{630}{8}=x$ (or $\frac{315}{4}=x$)

Thus, 7/8 of 90 is equal to 315/4 (or 78.75 in its decimal form).