What is 3/8 of 42?

How to calculate 3/8 of 42?

1. Multiply the whole number by the numerator of the fraction: 42 × 3 = 126
2. Divide this result by denominator of the fraction: 126/8 = 15.75
3. Simplify by dividing both the numerator and denominator by their GCD (2):
   • 126/2 = 63
   • 8/2 = 4
4. Which gives: 63/4

Since 63/4 is an improper fraction, the result could also be expressed as a mixed number: 15 3/4

How does it work?

The principle behind finding a fraction of a number, such as 3/8 of 42, is rooted in the method of cross-multiplication.

Consider the following proportion: $\frac{3}{8}=\frac{x}{42}$ (where x represents 3/8 of 42)

1. Using the cross-multiplication method, multiply both numerators by their opposite denominators: $3\times 42=8x$
2. Which gives: $126=8x$
3. Divide both sides by 8 to isolate x: $\frac{126}{8}=\frac{8x}{8}$
4. Which gives the result: $\frac{126}{8}=x$ (or $\frac{63}{4}=x$)

Thus, 3/8 of 42 is equal to 63/4 (or 15.75 in its decimal form).