No, a number ending in 0, 1, 4, 5, 6 or 9 is not always a square. While all square numbers do end with these digits, not every number with these digits is a square. For example, 26 ends in 6.
Class 8 Mathematics Chapter 1 A Square and A Cube question answer
Class 8 NCERT Ganita Prakash Chapter 1 A Square and A Cube solutions
Even though square numbers always end in 0, 1, 4, 5, 6 or 9, not all numbers ending in these digits are squares. For instance, 36 and 16 are squares ending in 6, but 26 also ends in 6 and is not a square. So, we cannot say a number is a square based only on its units digit. This rule only helps eliminate some possibilities, not confirm squareness.
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