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Step-5

Title: Area of semicircle

Grade: 7-a Lesson: S1-L4

Explanation:

Step	Type	Explanation	Answer
1	Problem	The area of a semicircle is \$1925cm^2\$. Find the radius?
2	Formula:	Area of a semicircle.	A = \$\frac{\pi r^2}{2}\$
3	Step	Substitute \$22/7\$ for \$pi\$ and 1925 for A .	1925 = \$\frac{\frac{22}{7} \times r^2}{2}\$
4	Step	Multiply.	\$1925 \times \frac{7}{22} \times 2 = r^2\$ \$\frac{26950}{22} = r^2\$
5	Step	Divide	\$\frac{\cancel26950^1225}{\cancel22^1} = r^2\$
6	Step	Solve for r	\$1225 = r^2\$ \$\sqrt{1225} = r\$ \$\sqrt{35^2} = r\$
7	Step	Answer	35 = r
8		Answer	The radius is \$35 cm\$.

Step

Type

Explanation

Answer

Problem

The area of a semicircle is \$1925cm^2\$. Find the radius?

Formula:

Area of a semicircle.

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

Step

Substitute \$22/7\$ for \$pi\$ and 1925 for A .

1925 = \$\frac{\frac{22}{7} \times r^2}{2}\$

Step

Multiply.

\$1925 \times \frac{7}{22} \times 2 = r^2\$
\$\frac{26950}{22} = r^2\$

Step

Divide

\$\frac{\cancel26950^1225}{\cancel22^1} = r^2\$

Step

Solve for r

\$1225 = r^2\$
\$\sqrt{1225} = r\$
\$\sqrt{35^2} = r\$

Step

Answer

35 = r

Answer

The radius is \$35 cm\$.