Why does this Math trick work?

Mathematics
Tutor: None Selected Time limit: 1 Day

STEP 1: Think of a number.

STEP 2: Double it.

STEP 3: Add 5.

STEP 4: Add 12.

STEP 5: Subtract 3.

STEP 6: Divide by 2.

STEP 7: Subtract your first number.

YOUR ANSWER SHOULD BE 7. WHY DOES THIS TRICK WORK?

May 5th, 2015

assume the origin number is x, 

step 2 2x

step 3+4+5: 2x+14

step 6: x+7 

and step 7: x 

you always go back x, that is the trick.  

May 5th, 2015


May 5th, 2015


May 5th, 2015


May 5th, 2015

assume the origin number is x, 

step 2 2x

step 3+4+5: 2x+14

step 6: x+7 

and step 7: x 

you always go back x, that is the trick.  


May 5th, 2015

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