If 25th term of an A.P. is 15 and if its 15th term is 25, then the 40th term of the A.P. is ______.

Question

Smart Achievers · Accepted Answer

(0)

Let $a$ be the first term and $d$ be the common difference.

According to question, $T_{25} = 15 \Rightarrow a + 24 d = 15$ ...(i)

$T_{15} = 25 \Rightarrow a + 14 d = 25$ ...(ii)

On solving (i) and (ii), we get $a = 39,$ $d = - 1$

So, $T_{40} = a + 39 d = 39 + 39 (- 1) = 0$

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