A quick way to square numbers that end in 5 using the formula

A quick way to square numbers that end in 5 using
the formula
BY ONE MORE THAN THE ONE BEFORE.

75² = 5625

75² means 75 x 75.

The answer is in two parts: 56 and 25.

The last part is always 25.

The first part is the first number, 7, multiplied
by the number "one more", which is 8:
so 7 x 8 = 56



Similarly 85² = 7225 because 8 x 9 = 72.


Try these:
1) 45² =

2) 65² =

3) 95² =

4) 35² =

5) 15² =