In an engineering college the average salary of all engineering graduates from Mechanical trade is Rs. 2.45 lacs per annum and that of the engineering graduates from Electronics trade is Rs. 3.56 lacs per annum. The average salary of all Mechanical and Electronics graduates is Rs. 3.12 lacs per annum. Find the least number of Electronics graduates passing out from this institute.-

Let the number of Mechanical Engineering graduates be M and the number of Electronics Engineering graduates be E.
Then,
  $$ \Rightarrow 2.45M + 3.56E = $$    $$3.12\left( {M + E} \right)$$
  $$ \Rightarrow 2.45M + 3.56E = $$    $$3.12M + 3.12E$$
$$\eqalign{ & \Rightarrow 0.44E = 0.67M \cr & \Rightarrow \frac{M}{E} = \frac{{0.44}}{{0.67}} = \frac{{44}}{{67}} \cr} $$
Since the ratio 44 : 67 is in its simplest form,
So least number of Electronics graduates = 67