Squaring a 2-digit number ending in 5

1. Choose a 2-digit number ending in 5.
2. Multiply the first digit by the next consecutive number.
3. The product is the first two digits: XX _ _.
4. The last part of the answer is always 25: _ _ 2 5.

   Example:

1. If the number is 35, 3 x 4 = 12 (first digit
   times next number). 1 2 _ _
2. The last part of the answer is always 25: _ _ 2 5.
3. So 35 x 35 = 1225.

   See the pattern?

1. For 65 x 65, 6 x 7 = 42 (first digit
   times next number): 4 2 _ _.
2. The last part of the answer is always 25: _ _ 2 5.
3. So 65 x 65 = 4225.