Probability
Full Member
- Joined
- Jan 26, 2012
- Messages
- 425
I remember this trick being played on me at school in the school playground. I never understood it then and I'm thinking that actually it does not work for every number as the author says.
Think of a number...10
Multiply it by 3..........30
Add 2............................32
Double the result.....64
Add 2............................66
Divide by 6.................11
Take away first number thought of...10
Answer = 1
Using algebra to do the same trick;
Think of a number
[MATH]{n}[/MATH]
Double it
[MATH]{2n}[/MATH]
Add 7
[MATH]{2n}+{7}[/MATH]
Double the result
[MATH]{2}({2n+7})={4n}+{7}[/MATH]
Add 6
[MATH]{4n}+{14}+{6}={4n}+{20}[/MATH]
Divide by 4
[MATH]\frac{4n+20}{4}=\frac{4n}{4}+\frac{20}{4}={n}+{5}[/MATH]
Take away the number first thought of;
[MATH]{n}+{5}-{n}={5}[/MATH]
The way I'm understanding this at the moment is that you end up with their number by using your own number but not your own thoughts of the number you thought of!
Look at my think of a number above, which is (10). That is the number I thought of. Enter that into the algebra and see the result, which will be their number (5), which is not the number I thought of!
Think of a number...10
Multiply it by 3..........30
Add 2............................32
Double the result.....64
Add 2............................66
Divide by 6.................11
Take away first number thought of...10
Answer = 1
Using algebra to do the same trick;
Think of a number
[MATH]{n}[/MATH]
Double it
[MATH]{2n}[/MATH]
Add 7
[MATH]{2n}+{7}[/MATH]
Double the result
[MATH]{2}({2n+7})={4n}+{7}[/MATH]
Add 6
[MATH]{4n}+{14}+{6}={4n}+{20}[/MATH]
Divide by 4
[MATH]\frac{4n+20}{4}=\frac{4n}{4}+\frac{20}{4}={n}+{5}[/MATH]
Take away the number first thought of;
[MATH]{n}+{5}-{n}={5}[/MATH]
The way I'm understanding this at the moment is that you end up with their number by using your own number but not your own thoughts of the number you thought of!
Look at my think of a number above, which is (10). That is the number I thought of. Enter that into the algebra and see the result, which will be their number (5), which is not the number I thought of!