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Step-1

Title: Perimeter of semicircle

Grade: 7-a Lesson: S1-L5

Explanation:

Step	Type	Explanation	Answer
1	Problem	The radius of a semicircle is 7cm. Find the perimeter.
2	Formula:	perimeter of a semicircle.	\$P = pi r + d\$ \$P = pi r + 2r\$ \$P = (pi + 2)r\$
3	Step	Substitute \$22/7\$ for \$pi\$ and 7 for r.	P = \$(\frac(22)(7) + 2)\times7\$
4	Step	Multiply.	P = \$(\frac(36)(7))\times7\$
5	Step	Cancel out common factor.	P = \$\frac(36)\cancel(7^1)\times\cancel(7)^1\$
6		Answer	The perimeter is \$36 cm\$.

Step

Type

Explanation

Answer

Problem

The radius of a semicircle is 7cm. Find the perimeter.

Formula:

perimeter of a semicircle.

\$P = pi r + d\$
\$P = pi r + 2r\$
\$P = (pi + 2)r\$

Step

Substitute \$22/7\$ for \$pi\$ and 7 for r.

P = \$(\frac(22)(7) + 2)\times7\$

Step

Multiply.

P = \$(\frac(36)(7))\times7\$

Step

Cancel out common factor.

P = \$\frac(36)\cancel(7^1)\times\cancel(7)^1\$

Answer

The perimeter is \$36 cm\$.