What is x when 42 divided by x equals 81?

To find the answer, just divide the dividend by the quotient: 42 ÷ 81 = 0.51851851851852

To prove this, let's compute 42 divided by 0.51851851851852: $\frac{42}{0.51851851851852} = 81$

How does it work?

Asking what the value of x could be when 42 divided by x gives a result of 81, is equivalent to solving the following equation:

$\frac{42}{x} = 81$

Multiply both sides by x: $\frac{42 x}{x} = 81 x$
$\frac{42 x}{x}$ is equivalent to $\frac{x}{x} \times 42$ , which simplifies to $1 \times 42$ (or just $42$ ).
Thus, the equation becomes: $42 = 81 x$
To find x, divide both sides by 81: $\frac{42}{81} = \frac{81 x}{81}$
Which gives, after simplification: $0.51851851851852 = x$ (or $x = 0.51851851851852$ )

So, if the dividend is 42 and the quotient is 81, the divisor is 0.51851851851852.