Originally Posted by

**Bingk** Um ... the way I did it is tedious. Basically, since abcd is a 4 digit number with distinct digits, I considered the set of all 4 digit perfect squares. We get that from $\displaystyle 32^2$ to $\displaystyle 99^2$ gives us this set.

From that set, we remove the ones with non-distinct digits, and we get the following list of numbers

1024,1089,1296,1369,1764,1849,1936,2304,2401,2601, 2704,2809,2916,3025,

3249,3481,3721,4096,4356,4761,5041,5184,5329,5476, 6084,6241,6724,7056,

7396,7569,7921,8649,9025,9216,9604,9801

We get the following pair:

1089,9801

Also, 9 * 1089 = 9801

* We are fortunate that none of the listed numbers ends in zero (i.e. d = 0), otherwise we would also have to consider 3 digit perfect squares, which would add more work ....