If 10th term of an AP is 97 and its 1st term is 2, find the sum of 15 terms
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Hi Mate!!!
10 th term is
2 + 9d = 97
Where 2 is ist term and d is common difference
=>. d = 95 /2
ist term is 2
2nd term is 2 + 95 / 2
3rd term is 2 + 2 ( 95 / 2 )
4th term is 2 + 3 ( 95 / 2 )
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15th term is = 2 + 14 ( 95 / 2 )
.............................................................................................
Sum of 15 terms = n / 2 { 2 a + ( n - 1 ) d }
n => no. of terms
d => common difference
a => ist term
=>. Sum of 15 terms = 15 / 2 { 4 + 14 ( 95 / 2 }
=>. Sum of 15 terms = 5017.5
Have a nice time
10 th term is
2 + 9d = 97
Where 2 is ist term and d is common difference
=>. d = 95 /2
ist term is 2
2nd term is 2 + 95 / 2
3rd term is 2 + 2 ( 95 / 2 )
4th term is 2 + 3 ( 95 / 2 )
.
.
.
15th term is = 2 + 14 ( 95 / 2 )
.............................................................................................
Sum of 15 terms = n / 2 { 2 a + ( n - 1 ) d }
n => no. of terms
d => common difference
a => ist term
=>. Sum of 15 terms = 15 / 2 { 4 + 14 ( 95 / 2 }
=>. Sum of 15 terms = 5017.5
Have a nice time
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