Squares · Beginner

Square numbers ending in 5

Multiply the leading part by its next integer, then append 25.

The fast method

⚡

3 × 4 = 12; append 25 → 1225

For 35², multiply 3 × 4 and append 25 to get 1225.

(10a+5)² = 100a(a+1)+25.

Use it when

The whole number must end in 5.

Watch out for

Only for integer squares ending in 5.

Example 1

3 × 4 = 12; append 25

1225

Example 2

6 × 7 = 42; append 25

4225

Example 3

9 × 10 = 90; append 25

9025