Carts and Wheels - Drawing Circles with a Compass

If the radius of a wooden cart wheel is $14\text{ cm}$, what is the length of its diameter?

Given: $Radius (r) = 14\text{ cm}$. We know the formula: $Diameter = 2 \times Radius$. $Diameter = 2 \times 14\text{ cm} = 28\text{ cm}$.

To find the diameter when the radius is known, we simply double the radius because the diameter consists of two radii joined in a straight line through the center.

Rohan used a compass to draw a circle. If the distance between the metal pointer and the pencil was $6\text{ cm}$, find the diameter of the circle.

The distance between the pointer and the pencil in a compass represents the radius. So, $r = 6\text{ cm}$. $Diameter = 2 \times r = 2 \times 6 = 12\text{ cm}$.

When using a compass, the opening width is the radius. We use the doubling rule ($2r$) to calculate the full width across the center.

$Radius (r) = 5\text{ cm}$ $Diameter (d) = 2 \times r$ $d = 2 \times 5 = 10\text{ cm}$ The diameter is $10\text{ cm}$.

Since the diameter of any circle is always double the radius, we multiply the given radius ($5\text{ cm}$) by $2$.

$Diameter (d) = 20\text{ m}$ $Radius (r) = \frac{d}{2}$ $r = \frac{20}{2} = 10\text{ m}$ The distance from the center to the rim is $10\text{ m}$.

The distance from the center to the rim is the radius. We find it by dividing the diameter by $2$.