The circumference of a circle is 440cm. Find the radius.

Circumference of a circle.

C = \$2 \pi r\$

Substitute \$22/7\$ for \$pi\$ and 440 for C.

440 = \$2\times\frac(22)(7)\timesr\$

Cancel out common factor.

\$\cancel{440}^40\$ = \$ 2 \times \frac{\cancel{22}^{2}}{7} \times r\$
40 = \$2\times\frac(2)(7)\timesr\$

\$\cancel{40}^20\$ = \$2\times\cancel{2}^1/7\timesr\$

20 = \$2\times\frac(1)(7)\timesr\$

\$\cancel{20}^10\$ = \$\cancel{2}^1\times1/7\timesr\$

10 = \$\frac(1)(7)\timesr\$

Multiply.

10 = \$\frac(1)(7)\timesr\$
\$10\times7\$ = r
70 = r
r = 70

Answer

The radius is \$70cm\$.