#### Square of a number ending with 5

Vivekanand Vellanki

0

Here's a technique I saw to square a number ending with 5.
Using an example to find 35^2. First write the low 2 digits - this is always 25. Next, multiply 3 (the number in the tenth place) with its successor (4) to get 12. Write 12 before 25 to get 35^2=1225.
Similarly, 45^2=2025 - 20=4*5 and 25 is the low 2 digits.How do I prove that this works for all numbers ending with 5?