# Three isotopes of an element have mass numbers m,m+1 and m+2.If the mean mass number is ( m +0.5) then which of the following ratios may be accepted for m,(m+1) and (m+2) in that order

$(a)\;1 : 1: 1\qquad(b)\;4 : 1: 1\qquad(c)\;3 : 2 : 1\qquad(d)\;2 : 1 : 1$

## 1 Answer

Average mass =$(m+0.5)=\large\frac{m\times 4+(m+1)\times 1+(m+2)\times 1}{6}$
$\Rightarrow \large\frac{6m+3}{6}$
Hence (b) is the correct answer.
answered Jan 16, 2014

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