Question

Solve for r in the proportion.

42/12 = 21/r


r =

Answer 1

To solve for \( r \) in the proportion \( \frac{42}{12} = \frac{21}{r} \), we can use cross-multiplication.

Cross-multiply the two fractions:

\[
42 \cdot r = 21 \cdot 12
\]

Now calculate \( 21 \cdot 12 \):

\[
21 \cdot 12 = 252
\]

Substituting this back into the equation gives:

\[
42r = 252
\]

Now, divide both sides by 42 to solve for \( r \):

\[
r = \frac{252}{42}
\]

Calculating the right side:

\[
r = 6
\]

Thus, the value of \( r \) is:

\[
\boxed{6}
\]