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  # A man weighs 100 kilograms plus half its own mass. What is his total mass?
  
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  A man weighs 100 kilograms plus half its own mass. What is his total mass?
  
  Guest Apr 19, 2015
  
  #2
  +1817
  +5
  
  $${\mathtt{M}} = {\mathtt{100}}{\mathtt{\,\small\textbf+\,}}{\frac{{\mathtt{M}}}{{\mathtt{2}}}}$$
  
  $${\mathtt{M}}{\mathtt{\,-\,}}{\frac{{\mathtt{M}}}{{\mathtt{2}}}} = {\mathtt{100}}$$
  
  $${\frac{{\mathtt{2}}{M}}{{\mathtt{2}}}}{\mathtt{\,-\,}}{\frac{{\mathtt{M}}}{{\mathtt{2}}}} = {\mathtt{100}}$$
  
  $${\frac{{\mathtt{M}}}{{\mathtt{2}}}} = {\mathtt{100}}$$
  
  $${\mathtt{M}} = {\mathtt{200}}$$
  
  gibsonj338  Apr 19, 2015
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  #1
  +26625
  +5
  
  Let M be the mass. Then
  
  M = 100 + M/2
  
  Subtract M/2 from both sides
  
  M/2 = 100
  
  Multiply both sides by 2
  
  M = 200 kg  (Heavy man!)
  
  .
  
  Alan  Apr 19, 2015
  #2
  +1817
  +5
  
  $${\mathtt{M}} = {\mathtt{100}}{\mathtt{\,\small\textbf+\,}}{\frac{{\mathtt{M}}}{{\mathtt{2}}}}$$
  
  $${\mathtt{M}}{\mathtt{\,-\,}}{\frac{{\mathtt{M}}}{{\mathtt{2}}}} = {\mathtt{100}}$$
  
  $${\frac{{\mathtt{2}}{M}}{{\mathtt{2}}}}{\mathtt{\,-\,}}{\frac{{\mathtt{M}}}{{\mathtt{2}}}} = {\mathtt{100}}$$
  
  $${\frac{{\mathtt{M}}}{{\mathtt{2}}}} = {\mathtt{100}}$$
  
  $${\mathtt{M}} = {\mathtt{200}}$$
  
  gibsonj338  Apr 19, 2015
  
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