In an A.P., the first term is 3 and the last term is 17. The sum of all the terms in the sequence is 70. Then the number of terms in the arithmetic sequence is

Question

In an A.P., the first term is 3 and the last term is 17. The sum of all the terms in the sequence is 70. Then the number of terms in the arithmetic sequence is (A) 7 (B) 5 (C) 9 (D) 6

Tardigrade Admin · Accepted Answer

(n/2)[t1+tn]=70 n[3+17]=140 n × 20=140 n=7

Q. In an A.P., the first term is $3$ and the last term is $17$ . The sum of all the terms in the sequence is $70$ . Then the number of terms in the arithmetic sequence is

7

5

9

6

8

$\frac{n}{2} [t_{1} + t_{n}] = 70$
$n [3 + 17] = 140$
$n \times 20 = 140$
$n = 7$

Q. In an A.P., the first term is 3 and the last term is 17. The sum of all the terms in the sequence is 70. Then the number of terms in the arithmetic sequence is

7

5

9

6

8

2n​[t1​+tn​]=70 n[3+17]=140 n×20=140 n=7

Q. In an A.P., the first term is $3$ and the last term is $17$ . The sum of all the terms in the sequence is $70$ . Then the number of terms in the arithmetic sequence is

$\frac{n}{2} [t_{1} + t_{n}] = 70$
$n [3 + 17] = 140$
$n \times 20 = 140$
$n = 7$