MATHEMATICS 49 



six significant figures (adding ciphers, if necessary, to make 

 six figures) and find between what two numbers in the 



column headed the significant figures of the given number 

 n 



fall; then proceed exactly as previously described to deter- 

 mine the fourth and fifth figures. 



EXAMPLE. (a) The reciprocal of 379.426 = ? (6) - = ? 



SOLUTION. (o) .379426 falls between .378788 = and 



.380228 = ^. The first difference is 380228-378788 

 2.03 



= 1440; the second difference is 380228-379426 = 802; 802 

 -4- 1440= .557, or .56. Hence, the first five significant figures 

 are 26356, and the reciprocal of 379.426 is .0026356, to five 

 significant figures. 



(&) .469200 falls between .469484 = -^ and .467290 



wb.lO 



= 2~TI' The fifSt difference is 2194 the second difference 

 is 284; 284 -* 2194 = . 129 + , or .13. Hence, 

 correct to five significant figures. 



MENSURATION 



In the following formulas, unless otherwise stated, the 

 letters have the meanings here given: 

 D = larger diameter; 

 <i = smaller diameter; 

 R = radius corresponding to D; 

 r = radius corresponding to d; 

 p = perimeter of circumference; 

 C = area of convex surf ace = area of flat surface that can 



be rolled into the shape shown; 



S = area of entire surf ace = C+ area of the end or ends; 

 A = area of plane figure; 

 w = 3.1416, nearly = ratio of any circumference to its 



diameter; 



V = volume of solid. 

 The other letters used will be found on the cuts. 



