Objective:

To calculate the area of a circle.

General:

The formula to calculate the area of a circle is given by:

The area is calculated using a combination of the A, B, C and D scales.

Method:

• Align the C index with the radius on the D scale. (You will also see the B index aligned with the square on A.)
• Move the cursor to Bπ (π on the B scale).
• Read the result on the A scale.

 

Example: Calculate the area of a circle with radius 2.5 cm.

• Align C1 with D2.5
• Move the cursor to Bπ
• Read result A19.6

Hence the area of the circle is 19.6 cm².

 

Practice Questions:  Calculate the area of the following circles.

1. d=5.8" (Ans: 26.4 in²)
2. r= 7.2 cm (Ans: 163 cm²)