Medium INTEGER +4 / -1 PYQ · JEE Mains 2023

$50^{\text {th }}$ root of a number $x$ is 12 and $50^{\text {th }}$ root of another number $y$ is 18 . Then the remainder obtained on dividing $(x+y)$ by 25 is ____________.

Answer (integer) 23

Solution

<p>Given ${x^{{1 \over {50}}}} = 12 \Rightarrow x = {12^{50}}$</p> <p>${y^{{1 \over {50}}}} = 18 \Rightarrow y = {18^{50}}$</p> <p>$12\equiv13$ (Mod 25)</p> <p>$12^2\equiv19$ (Mod 25)</p> <p>$12^3\equiv-3$ (Mod 25)</p> <p>$12^9\equiv-2$ (Mod 25)</p> <p>$12^{10}\equiv-1$ (Mod 25)</p> <p>$12^{50}\equiv-1$ (Mod 25) ..... (i)</p> <p>Now</p> <p>$18\equiv7$ (Mod 25)</p> <p>$18^2\equiv-1$ (Mod 25)</p> <p>$18^{-50}\equiv-1$ (Mod 25) ..... (ii)</p> <p>$\therefore$ $12^{50}+18^{50}\equiv-2$ (Mod 25)</p> <p>$\equiv23$ (Mod 25)</p> <p>$\therefore$ Answer = 23</p>

About this question

Subject: Mathematics · Chapter: Binomial Theorem · Topic: Binomial Expansion

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