Multiply by 15

Squaring any number that ends in 5 is a simple two-step process:

1. Multiply the first digit by the next higher digit. For example, for (35)², calculate:
   3 × 4 = 12
2. Append 25 to the result from step 1. Therefore:
   35² = 1225 = 1225

With this quick trick, squaring numbers like 15, 25, 35, and so on becomes effortless!