Lesson Example Discussion Quiz: Class Homework |
Step-4 |
Title: Area of circle |
Grade: 7-a Lesson: S1-L2 |
Explanation: |
| Step | Type | Explanation | Answer |
|---|---|---|---|
1 |
Problem |
The diameter of a circle is 18cm. Find the area. |
|
2 |
Formula: |
Radius of a circle. |
r = \$d/2\$ |
3 |
Step |
Substitute 18 for d. |
r = \$\cancel{18}^9/\cancel{2}^1\$ r = 9 |
4 |
Step |
Radius. |
\$r = 9\$ |
5 |
Formula: |
Area of a circle. |
A = \$pi r^2\$ |
6 |
Step |
Substitute \$22/7\$ for \$pi\$ and 9 for r. |
A = \$\frac(22)(7) (9)^2\$ |
7 |
Step |
Multiply. |
A = \$\frac(22)(7)\times(9)\times(9)\$ A = \$\frac(22)(7)\times(81)\$ A = \$\frac(22\times81)(7)\$ A = \$\frac(1782)(7)\$ |
8 |
Step |
Divide. |
A = \$\frac(1782)(7)\$ A = \$\cancel{1782}^254.57/\cancel{7}^1\$ A = 254.57 |
9 |
Answer |
The area is \$254.57 cm^2\$. |
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