Question

Let $\ast$ be a 'binary' operation of $N$ given by $a\ast b=LCM(a,b)$ for all $a,b\in N$. Find $5\ast 7.$

Answer 1

$a\ast b=LCM(a,b)$ for all $a,b\in N$

Here, $a=5,b=7$

Thus, $5\ast 7=LCM(5,7)=5\times 7=35$ (Since the two numbers are co-prime, their LCM becomes their product)