How do you calculate areas to 1 decimal place for a circle?

The area of a circle is calculated by multiplying pi by r2. Where r = the radius of the circle.

IF we use 3.1416 as our value of pi, this means that a circle with a radius of 1 inch has an area of 3.1416 square inches. Rounding this to one decimal place gives us 3.1 square inches.

Other radius - area ratiOS are

2 .......... 12.5665 - rounded = 12.6

3 .......... 28.2744 - rounded = 28.3

4 .......... 50.2656 - rounded = 50.3

5 .......... 78.54 - - - rounded = 78.5

6 ......... 113.0976 - rounded = 113.1

7 ......... 153.9384 - rounded = 153.9

8 ......... 201.0624 - rounded = 201.1

9 ......... 254.4696 - rounded = 254.5

10 ....... 314.16 - - - rounded = 314.2