**Q) If the mth term of an AP is 1/n and the nth term is 1/m, then show that the sum of (mn)th term is (mn+1).**

**Ans: **

Let first term of the given AP = a

Common difference of the given AP = d

Then,

…………….(I)

…………….(ii)

Subtracting equation (ii) from equation (ii),we get

Putting in equation (i), we get

Next, we know that the sum of n terms of an AP is given by:

Therefore the sum of mn terms will be given by:

By substituting values of a and d in the above formula, we get:

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