Q. Let p be a two-digit number aand q be the number consisting of same digits written in reverse order. If p × q = 2430, then what is the difference between p and q?

Explanation : 

Difference between p and q

Let’s say that p = 10x + y and q = 10y + x where x and y are digits.

Then p × q = (10x + y)(10y + x) = 100xy + 10xy + 10xy + xy = 2430. Simplifying this equation gives us xy = 2430/121 = 20.

Since x and y are digits, the only possibility is that x=5 and y=4 or vice versa. Therefore p=54 and q=45 or vice versa. The difference between p and q is |54-45|=9.