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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
+1851
+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
#1
+26969
+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
+1851
+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