$50^{\text {th }}$ 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
This question is part of PrepWiser's free JEE Main question bank. 193 more solved questions on Binomial Theorem are available — start with the harder ones if your accuracy is >70%.