Question

substitute the given values into the given formula and solve for the unknown variable. if necessary, round to one decimal place. (use the approximation 3.14 for π.) c = 2πr; c = 78.5 (circumference of a circle)

Explanation:

Step1: Write the formula

The formula for the circumference of a circle is $C = 2\pi r$. We are given that $C=78.5$ and $\pi\approx3.14$.

Step2: Solve for $r$

Substitute the values into the formula: $78.5 = 2\times3.14\times r$. First, simplify the right - hand side: $2\times3.14 = 6.28$, so the equation becomes $78.5=6.28r$. Then, divide both sides of the equation by $6.28$ to isolate $r$: $r=\frac{78.5}{6.28}$.

Step3: Calculate the value of $r$

$\frac{78.5}{6.28}=12.5$.

Answer:

$12.5$