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Skip to 0 minutes and 0 secondsAre 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?

Skip to 0 minutes and 11 secondsOrel: Yes!

Skip to 0 minutes and 11 secondsYossi: 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?

Skip to 0 minutes and 20 secondsOrel: No!

Skip to 0 minutes and 20 secondsYossi: OK!! I'm going to show you. I want you to... ...choose any number ending in a 5, so, 15, 125, whatever.

Skip to 0 minutes and 30 secondsOrel: 45

Skip to 0 minutes and 31 secondsYossi (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?

Skip to 0 minutes and 45 secondsOrel: OK!

Skip to 0 minutes and 45 secondsYossi: Go! 45 squared is 2025! (repeats) 2025

Skip to 0 minutes and 50 secondsOrel: Oh my God! True?

Skip to 0 minutes and 52 secondsOrel: Yes!

Skip to 0 minutes and 52 secondsYossi: Let's try another one then... Give me another number. Any number ending in 5.

Skip to 0 minutes and 58 secondsOrel: 85.

Skip to 0 minutes and 58 secondsYossi: 85. Thats... go on square it... 7225!

Skip to 1 minute and 5 secondsOrel: whoa! How do you do that?

Skip to 1 minute and 9 secondsYossi: You wish you knew, ha?

Skip to 1 minute and 11 secondsOrel: Yes!

Skip to 1 minute and 11 secondsYossi: 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!

A Lightning Calculator Magic Trick

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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This video is from the free online course:

An Introduction to Recreational Math: Fun, Games and Puzzles

Weizmann Institute of Science

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