513=n%2(108+(n-1)-3)

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Posted by Aniesh G 6 years, 10 months ago
- 5 answers
Gaurav Seth 6 years, 10 months ago
54, 51, 48,...........
First term a = 54
Common difference d = 51 - 54 = -3
Let n is the number of terms.
Given, sum = 513
=> (n/2)*{2a + (n - 1)d} = 513
=> n{2a + (n - 1)d} = 513*2
=> n{2*54 + (n - 1)*(-3)} = 1026
=> n{108 - 3n + 3} = 1026
=> n{111 - 3n} = 1026
=> 111n - 3n2 = 1026
=> 3n2 - 111n + 1026 = 0
=> n2 - 37n + 342 = 0 {divide by 3}
=> (n - 18)*(n - 19) = 0
=> n = 18, 19
Hence, number of terms is either 18 or 19
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Ritika Bisht 6 years, 10 months ago
0Thank You