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February 1st, 2015, 10:40 PM  #1 
Newbie Joined: Nov 2014 From: Tamilnadu Posts: 5 Thanks: 0  Can you find it???
Hi I wanted to share an interesting trick which i have read in a site. You can play this trick with your friends and prove your intelligence...... Ready???? Let's start Ask your friend to think of a number. Let him/her follow the below steps. 1. Add 2 with the number 2. Multiply result with 5. 3. Add 3 with the answer. 4. Multiply 2 to the resultant number and add it with four. 5. Divide the answer with 10. Now if your friend says the resultant value, you can guess the number thought by your friend!!!!! Wanna know how???? Give gap and think...... Still din find out??????Check out here : Magic Number 3 Trick 
February 2nd, 2015, 05:44 AM  #2  
Banned Camp Joined: Jun 2014 From: Earth Posts: 945 Thanks: 191  Quote:
 
February 2nd, 2015, 05:52 AM  #3 
Global Moderator Joined: Dec 2006 Posts: 20,619 Thanks: 2074 
Your annotations feature some mistakes.

February 3rd, 2015, 08:22 AM  #4  
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 14,412 Thanks: 1024  Quote:
{2[5(n + 2) + 3] + 4} / 10 = (10n + 30) / 10 = 10(n + 3) / 10 = n + 3 So result always 3 more than the guessed number.  
February 3rd, 2015, 11:55 AM  #5 
Banned Camp Joined: Jun 2014 From: Earth Posts: 945 Thanks: 191 
Originally Posted by Smrithi View Post Hi I wanted to share an interesting trick which i have read in a site. You can play this trick with your friends and prove your intelligence...... Ready???? Let's start Ask your friend to think of a number. Let him/her follow the below steps. Let N = the guessed number. 1. Add 2 with the number N + 2 2. Multiply result with 5. 5(N + 2) = 5N + 10 3. Add 3 with the answer. 5N + 10 + 3 = 5N + 13 4. Multiply 2 to the resultant number and add it with four. 2(5N + 13) + 4 = 10N + 26 + 4 = 10N + 30 5. Divide the answer with 10. $\displaystyle \dfrac{10N + 30}{10} = N + 3$ N + 3 = three more than the guessed number. Now if your friend says the resultant value, you can guess the number thought by your friend!!!!! Last edited by Math Message Board tutor; February 3rd, 2015 at 12:00 PM. 
February 3rd, 2015, 01:34 PM  #6 
Math Team Joined: May 2013 From: The Astral plane Posts: 2,152 Thanks: 875 Math Focus: Wibbly wobbly timeywimey stuff. 
It's a nice little trick. It's even more fun in base 3. Dan 
February 3rd, 2015, 02:48 PM  #7 
Global Moderator Joined: Dec 2006 Posts: 20,619 Thanks: 2074 
Alternatively, multiply by 10, then subtract 4, then divide by 2, etc. There is a better version of the trick that uses steps that cannot be "reversed" in that way to obtain the number used.

February 3rd, 2015, 05:12 PM  #8 
Senior Member Joined: Aug 2014 From: United States Posts: 137 Thanks: 21 Math Focus: Learning  
February 3rd, 2015, 07:35 PM  #9 
Global Moderator Joined: Dec 2006 Posts: 20,619 Thanks: 2074 
I forget its precise details, but it involved asking the user to introduce a second number of limited size, such as a year. The calculations had the effect of concatenating the two numbers. To make that unobvious, the number to be subtracted at the end was a 3digit number.

February 3rd, 2015, 08:14 PM  #10 
Math Team Joined: Dec 2013 From: Colombia Posts: 7,650 Thanks: 2630 Math Focus: Mainly analysis and algebra 
I remember reading of one that involved getting three people to think of a number each. You take the first, do some operations, add in the second, do more operations, add in the third and do some more operations. Again, I believe there was a threedigit subtraction to be done to get the three numbers back again.


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