how many terms of the series 54,51,48....... be taken so that their sum is 513?
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In this series
First term= a= 54
Common difference= d =51-54= -3
Sum =513
n/2 (2a + (n-1)d) = 513
108n -3n^2 +3n = 1026
3n^2-111n+ 1026=0
Solving this eqn we get n=18
First term= a= 54
Common difference= d =51-54= -3
Sum =513
n/2 (2a + (n-1)d) = 513
108n -3n^2 +3n = 1026
3n^2-111n+ 1026=0
Solving this eqn we get n=18
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