# math

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For the arithmetic series 13+19+...

a. find tsub27
b. find Ssub27
c. if tsubn = 445, find n

• math -

a=13
d=6
T27 = 13+26*6 = 169
S27 = 27/2 (2*13 + 26*6) = 2457

445 = 13 + (n-1)6
n=73

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