To square any number ending with 5.
Formula : (A5)² = A(A+1)/25
Getting the square of a number ending in 5 is very simple. If the last digit of the number is 5, the last two digit of the square will be 25. Whatever is the earlier part of the number multiply it with one more than itself and that will be the first part of the answer.
(1) (25)² = 2 (2+1)/25 = 6/25 = 625
(2) (35)² = 3 (3+1)/25 = 12/25 = 1225
(3) (45)² = 4 (4+1)/25 = 20/25 = 2025
(4) (85)² = 8 (8+1)/25 = 72/25 = 7225
(5) (95)² = 9 (9+1)/25 = 90/25 = 9025
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