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# Squaring Numbers Ending in 5

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How do you square two-digit numbers ending in 5, using only your mind? This slideshow will show you how!

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### Squaring Numbers Ending in 5

1. 1. Squaring Numbers Ending in 5 <ul><li>Presented by Grey Matters Mental Gym </li></ul><ul><li>http://members.cox.net/beagenius/ </li></ul>
2. 2. Squaring Numbers Ending in 5 <ul><li>Squaring a number is simply multiplying it by itself. For example, 8 squared (8 2 ) is simply 8 * 8, or 64. Conversely, the square root of 64 would be 8. </li></ul><ul><li>Squaring numbers ending in 5 are particularly easy. It’s also useful in extracting the square root of any number. </li></ul>
3. 3. Squaring Numbers Ending in 5 <ul><li>Have a spectator give you any number from 1 to 100 that ends in 5. </li></ul><ul><li>Imagine being able to figure the square of that number in your head! </li></ul>
4. 4. Squaring Numbers Ending in 5 Requirements <ul><li>Calculator </li></ul><ul><li>Spectator </li></ul>
5. 5. Squaring Numbers Ending in 5 <ul><li>To be able to square numbers ending in 5 mentally, you must know your times tables up to 10 times 10. </li></ul>
6. 6. Squaring Numbers Ending in 5 <ul><li>When you’re given a two-digit number ending in 5, focus on the digit in the tens place. </li></ul><ul><li>For example, let’s say you’re given the number 35. In this case, you would focus on the 3. </li></ul>
7. 7. Squaring Numbers Ending in 5 <ul><li>Simply multiply the tens digit by a number 1 higher than itself. </li></ul><ul><li>Since we’re focusing on the “3” in 35, we would multiply 3 time 4 (1 higher than 3) to get 12. </li></ul>
8. 8. Squaring Numbers Ending in 5 <ul><li>To finish, simply add “25” to the end of the number you just calculated. That’s the answer! </li></ul><ul><li>Taking 35, we focused on the “3”, multiplying 3 times 4 to get 12. Adding “25” to the end gives 1,225, which is the answer to 35 squared (35 2 ). </li></ul>
9. 9. Squaring Numbers Ending in 5 <ul><li>Other examples: </li></ul><ul><li>What is 75 2 ? 7 times 8 is 56, so the answer is 5,625. </li></ul>
10. 10. Squaring Numbers Ending in 5 <ul><li>Other examples: </li></ul><ul><li>What is 85 2 ? 8 times 9 is 72, so the answer is 7,225. </li></ul>
11. 11. Squaring Numbers Ending in 5 <ul><li>Other examples: </li></ul><ul><li>What is 95 2 ? 9 times 10 is 90, so the answer is 9,025. </li></ul>