In this type of questions

**First you see them in their original number.**

Example - 64 * 81

8 * 9 (64 is the square of 8 and 81 is the square of 9)

**After that, 72 (square it)**

**= 5184**

Example - 144 * 169 =

12^2 * 13^2 = (12*13)^2 =156^2 = 24336

Example - 256 * 441 =

16^2 * 21^2 = (16*21)^2= 336^2 = 112896