18 APPLIED SCIENCE 



0.845 

 4.5 



34225 

 27380 



30.8025 



Since 5 may be in error, any part of the partial product involving 

 5 may also be in error. Therefore it is doubtful whether any figure 

 to the right of the first of the result (which is in doubt) should 

 be retained.* 



21. Rules for Finding Area and Volume. The forms of 

 most tanks, compartments, and mechanical parts are those 

 of simple geometrical figures such as squares, rectangles, 

 hexagons, ellipses, and circles. Every pupil should be able 

 to find the area and volume of such figures quickly and 

 accurately. The following rules will be of assistance: . 



RULES RELATIVE TO THE CIRCLE 



To Find Circumference: 



Multiply diameter by 3.1416 

 Or divide diameter by .3183 



To Find Diameter: 



Multiply circumference by .3183 

 Or divide circumference by 3.1416 



To Find Radius: 



Multiply circumference by .15915 

 Or divide circumference by 6.28318 



To Find Area: 



Multiply circumference by one-quarter of the diameter 



* For a more extended discussion of practical mathematics see 

 " Vocational Mathematics," by William H. Dooley. 



