Formulation of L.P Model
Let $${x}_{1},{x}_{2}$$ and $${x}_{3}$$ denote the number of units of products $$A,B$$ and $$C$$ to be manufactured .
Objective is to maximize the profit.
i.e., maximize $$Z=90{x}_{1}+40{x}_{2}+30{x}_{3}$$
Constraints can be formulated as follows:
For raw material $$P, 6{x}_{1}+5{x}_{2}+2{x}_{3}\le5,000$$
For raw material $$Q, 4{x}_{1}+7{x}_{2}+3{x}_{3}\le6,000$$
Product $$B$$ requires $$\frac{1}{2}$$ and product $$C$$ requires $${\left(\frac{1}{3}\right)}^{rd}$$ the time required for product $$A.$$
Then $$\frac{t}{2}$$ and $$\frac{t}{3}$$ are the times in hours to produce $$B$$ and $$C$$ and since $$1,600$$ units of $$A$$ will need time $$1,600t$$ hours, we get the constraint,
$$t{x}_{1}+\frac{t}{2}{x}_{2}+\frac{t}{3}{x}_{3}\le 1,600t$$ or
$${x}_{1}+\frac{{x}_{2}}{2}+\frac{{x}_{3}}{3}\le1,600$$ or
$$6{x}_{1}+3{x}_{2}+2{x}_{3}\le9,600$$
Market demand requires
$${x}_{1}\ge300, {x}_{2}\ge250,$$ and $${x}_{3}\ge200$$
Finally, since products $$A,B$$ and $$C$$ are to be produced in the ratio $$3:4:5,$$
$${x}_{1}:{x}_{2}:{x}_{3}::3:4:5$$
or $$\frac{{x}_{1}}{3}=\frac{{x}_{2}}{4},$$
and $$\frac{{x}_{2}}{4}=\frac{{x}_{3}}{5}.$$
Thus, there are two additional constraints
$$4{x}_{1}-3{x}_{2}=0$$ and $$5{x}_{2}-4{x}_{3}=0$$ where $${x}_{1},{x}_{2},{x}_{3}\ge0$$