Q4
Number Theory
GCD, LCM, and Coprimality
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Let $X = \{0,1,2,3,\ldots,99\}$. For $a, b$ in $X$, we define $a * b$ to be the remainder obtained by dividing the product $ab$ by 100. For example, $9 * 18 = 62$ and $7 * 5 = 35$. Let $x$ be an element in $X$. An element $y$ in $X$ is called the inverse of $x$ if $x * y = 1$. Find all elements of $X$ that have inverses and write down their inverses.