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Title: Perimeter of semicircle

Grade: 7-a Lesson: S1-L5

Explanation:

Step	Type	Explanation	Answer
1	Problem	The radius of a semicircle is 35m. 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 35 for r.	P = \$(\frac(22)(7) + 2)\times35\$
4	Step	Add.	P = \$(\frac(22 + 14)(7))\times35\$
5	Step	Multiply.	P = \$(\frac(36)(7))\times35\$
6	Step	Cancel out common factor.	P = \$(\frac(36)(\cancel(7)^1))\times\cancel(35)^5\$
7	Step	Multiply.	\$P = 180 \$
8		Answer	The perimeter is \$180 m\$

Step

Type

Explanation

Answer

Problem

The radius of a semicircle is 35m. 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 35 for r.

P = \$(\frac(22)(7) + 2)\times35\$

Step

Add.

P = \$(\frac(22 + 14)(7))\times35\$

Step

Multiply.

P = \$(\frac(36)(7))\times35\$

Step

Cancel out common factor.

P = \$(\frac(36)(\cancel(7)^1))\times\cancel(35)^5\$

Step

Multiply.

\$P = 180 \$

Answer

The perimeter is \$180 m\$