Do you know its Property-3

Algebra Level 5

$a_n$ is the nth term of an increasing arithmetic progression. If $\sum_{r=1}^{4000}\frac{1}{a_r a_{r+1}}=10$ and $a_{2001}=25$ , what is the value of $|a_1-a_{4001}|$ ?

You can try more such problems of the set Do you know its property ?