Question

Sum of the second and ninth terms of an arithmetic sequence is 42. What is the sum of first 10 terms?​

Answer 1

Hey friend ,

Here is your Answer

Assuming the first term to be `a` and the common difference to be `d`.

nth term is given by a + (n-1)d

Thus:

a+3d +a +5d = 42 ; a+4d=21

a+2d + a + 8d =52; a+5d= 26

Therefore, d=5 and a=1.

First term is, a=1

Tenth term is, a+9d= 46

Sum of first 10 terms = 10/2*(1+46) = 235

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