Here’s a really easy way to calculate the squares of numbers ending with a 5… suppose we are taking the square of 85:

85 * 85 = 7225

Now, the easiest way of doing this is by taking the part of the number without the last “5” in it.. which in this example would be simply 8. Now, multiply 8 by the next number, which is 9. We get a 72… just add a 25 at the end of it and you get the answer: 7225

Therefore, as a general equation we have:

105 * 105 = (10 * 11) with a 25 at the end = 11025

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