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Step-1

Title: Area of semicircle

Grade: 7-a Lesson: S1-L4

Explanation:

Step	Type	Explanation	Answer
1	Problem	The radius of a semicircle is 7cm. Find the area
2	Formula:	Area of a semicircle	A = \$\frac{\pi r^2}{2}\$
3	Step	Substitute \$22/7\$ for \$pi\$ and 7 for r	A = \$\frac{\frac{22}{7}\times(7)^2}{2}\$ A = \$\frac{\frac{22}{7} \times 7 \times 7}{2}\$
4	Step	Cancel out common factor.	A = \$\frac{\frac{22}{\cancel{7}^1} \times \cancel{7}^1 \times 7}{2}\$
5	Step	Multiply.	A = \$\frac{\frac{22}{1} \times 1 \times 7}{2}\$ A = \$\frac{22 \times 1 \times 7}{2}\$
6	Step	Divide.	A = \$\frac(154)(2)\$ A = \$\frac(\cancel(154)^77)(\cancel(2)^1)\$
7	Step	Answer.	A = 77
8		Answer	The area is \$77 cm^2\$.

Step

Type

Explanation

Answer

Problem

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

Formula:

Area of a semicircle

A = \$\frac{\pi r^2}{2}\$

Step

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

A = \$\frac{\frac{22}{7}\times(7)^2}{2}\$
A = \$\frac{\frac{22}{7} \times 7 \times 7}{2}\$

Step

Cancel out common factor.

A = \$\frac{\frac{22}{\cancel{7}^1} \times \cancel{7}^1 \times 7}{2}\$

Step

Multiply.

A = \$\frac{\frac{22}{1} \times 1 \times 7}{2}\$
A = \$\frac{22 \times 1 \times 7}{2}\$

Step

Divide.

A = \$\frac(154)(2)\$
A = \$\frac(\cancel(154)^77)(\cancel(2)^1)\$

Step

Answer.

A = 77

Answer

The area is \$77 cm^2\$.