...= a, y(s +*)=*, s(* + y) = c. (30) 49. Explain how to find the sum of an arithmetical progression, when the first term, the common difference, and the number of terms are given. Given the series 1 + 3 + 5 + . . . + (a" - 5) 4 (2" - 3) + (2" - 1) find (a) the number of terms, (b)...

...(II), we obtain the following convenient formula for finding the sum of an arithmetical progression when the first term, the common difference, and the number of terms are known. That is : 405. The first term (a), the common difference (d), the number of terms (n), the last...

...'d, s = ?[2a+(nl)d]. (3) From formula (3) the sum of an arithmetical progression may be calculated if the first term, the common difference, and the number of terms are given. Formula (3) may be written. 8 = or, since a + (n — l)d = l, s = -°(a+Z). (4) ILLUSTRATION 1: Find...

...examples. What are tho extremes t The means' ART. 300. In every arithmetical scries, five things are considered: 1st, the first term ; 2d, the last term;...last yd. cost? SOLUTION. — To find the cost of the second yard, add 4 cts. once to the cost of the first; to find the cost of the third, add 4 cts. twice...

...terms and the number of terms are known. The second formula is used for finding the sum of n terms when the first term, the common difference and the number of terms are given. Worked Examples. 67. Ex. 1. Find the sum of the arithmetic series in which the first term is Г8, the...