Question

10th term of an AS is 100.what is the sum of 7th and 13th term

Answer 1

Answer:

200

Step-by-step explanation:

Let the first term of the AS = a

"        "     common difference of the AS = d

Now, we know that, $a_{n}$ = a + ( n-1)d

so, $a_{10}$ = a + 9d

or a + 9d = 100....................(i)

$a_7$ = a + 6d

and $a_{13}$ = a + 12d

So, $a_7$ +  $a_{13}$ = a + 6d + a + 12d= 2a + 18d

or $a_7$ +  $a_{13}$ = 2 (a +9d)

or $a_7$ +  $a_{13}$  = 2 × 100 (using (i) )

∴ $a_7$ +  $a_{13}$  = 200

Hope this is helpful. Please rate the answer!