CIRCLES. 



To find the circumference of a circle. 



RULE 1. Multiply the diameter by 3.1416, and the pro- 

 duct will be the circumference. 



RULE 2. Or, as 7 is to 22 so is the diameter to the cir- 

 cumference. 



EXAMPLE. What is the circumference of a circle whose 

 diameter is 25 ? 



SOLUTION. 25x3.1416=78.54:. Ans. By Rule 2. 7 : 

 22:: 25 : 78.5. Ans. 



To find the diameter of a circle. 



RULE 1. Divide the circumference by 3.1416, and the- 

 quotient will be the diameter. 



RULE 2. Or, as 22 is to 7, so is the circumference to the 

 diameter. 



EXAMPLE. What is the diameter of a circle whose cir- 

 cumference is 69.11 ? 



SOLUTION. 69.11-7-3.1416=22. Ans. By Rule 2. 22 : 

 7:: 69.11 : 22. Ans. 



To find the area of a circle. 



RULE 1. Multiply the square of the diameter by .7854, 

 or the square of the circumference by .07958, and the pro- 

 duct will be the area. 



