This is a tricky sequence and series question from the Black Book for JEE Mains and Advanced.

This question is conceptually wrong but you'll learn a lot from the solution to this question and can use it in JEE Maths.

You can also expect this or similar JEE Maths questions in JEE Advanced exam.

The question reads:-

Let X1, X2, X3,......, Xk be the divisors of positive integer 'n' ( Including 1 and n ). if X1 + X2 + X3 + ........ + Xk = 75 k/∑/i=1 (1/X1) is equal to :

a. 75/k
b. 75/n
c. 1/n
d. 1/75

To answer why this maths question from Black Book is wrong, the sum of divisors of any positive integer is not 75 which is given in the question.

If we ignore this and consider a hypothetical case, we can solve this question.

We can use properties of divisors and find the answer to this sequence and series question from Black Book for JEE Mains and Advanced.

Can you solve this JEE Advanced level question from the Black Book?

Give it an attempt to solve yourself.

If you are not able to solve it, stay with us during the course of this video and you'll learn the solution and important concepts.

Stay tuned with @BHANNATMATHS

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