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A Lightning Calculator Magic Trick

Watch Yossi Elran perform a math magic trick
Are you ready for your second magic trick? This time I’m going to amaze you, with my fast as lightning brain! Orel is going to help us in this trick as well, right Orel?
Orel: Yes!
Yossi: Orel has a calculator with her. Now I’m going to show you how I can do some lightning calculations in my head. Do you believe that?
Orel: No!
Yossi: OK!! I’m going to show you. I want you to… …choose any number ending in a 5, so, 15, 125, whatever.
Orel: 45
Yossi (repeats): 45 So what I’m going to ask you to do, when I say “Go!” is to try and square the number on your calculator, that is, do 45 times 45. Before you tell me the answer I’m going to tell you the answer, OK?
Orel: OK!
Yossi: Go! 45 squared is 2025! (repeats) 2025
Orel: Oh my God! True?
Orel: Yes!
Yossi: Let’s try another one then… Give me another number. Any number ending in 5.
Orel: 85.
Yossi: 85. Thats… go on square it… 7225!
Orel: whoa! How do you do that?
Yossi: You wish you knew, ha?
Orel: Yes!
Yossi: You wish you knew, well… See, the magic that I do in this course, it’s all based on math. You wish you knew… but I’m not going to tell you. It’s for you to try and find out and work out the math behind the magic. Can you do it? Let’s see!

Can you uncover the secret behind Yossi’s lightning calculator magic trick? Post your ideas below!
The correct answer will be disclosed in the weekly email…

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An Introduction to Recreational Math: Fun, Games, and Puzzles

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