A classroom consists 13 equidistant desks. If nitrous oxide(laughing gas) is released from the first desk and tear gas C6H11OBr is released from last desk. Find out the desk from 1st at which student starts laughing and weeping simultaneously. No links please

Dear Student,

One row = 1 metre.
From the above diagram and information
13 equidistant row = 12 m distance

Given :

Distance from N2O 
D1 = X
Distance from weeping gas
D2= 12-X
Molecular weight of  N2O
M1 =  44 g/mol
Molecular weight of  C6H11OBr
M2 = 179 g/mol  

Formula use :
(D1/D2) =  (M2/M1)1/2 

Answer :
(x/12-x) = (179/44 )1/2 
x/12-x = (4.)1/2 
x/12-x =  2

On solving
X = 8 m
Hence, to cover 8 m, the row will be 9th ( please count using diagram ) i.e the desk from where  laughing and weeping simultaneously occur will be row 9th desk.  

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