In the given figure, feasible region represented by the constraints $4x + y ≥80, x+5y≥ 115, 3x + 2y ≤ 150, x, y ≥ 0$ is
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Region C
Given constraints
$4x+y\ge80$
$x+5y\ge115$
$3x+2y\le150$
$x\ge0,\;y\ge0$
Find intersection points of boundary lines
Intersection of $4x+y=80$ and $x+5y=115$
$y=80-4x$
$x+5(80-4x)=115$
$x+400-20x=115$
$-19x=-285$
$x=15$
$y=20$
Point $(15,20)$
Intersection of $4x+y=80$ and $3x+2y=150$
$y=80-4x$
$3x+2(80-4x)=150$
$3x+160-8x=150$
$-5x=-10$
$x=2$
$y=72$
Point $(2,72)$
Intersection of $x+5y=115$ and $3x+2y=150$
$x=115-5y$
$3(115-5y)+2y=150$
$345-15y+2y=150$
$-13y=-195$
$y=15$
$x=40$
Point $(40,15)$
Intersection with axes
From $4x+y=80$, at $x=0$, $y=80$ but does not satisfy $x+5y\ge115$
From $x+5y=115$, at $y=0$, $x=115$ but violates $3x+2y\le150$
From $3x+2y=150$, at $x=0$, $y=75$ but violates $x+5y\ge115$
Hence feasible corner points are
$(2,72),\;(15,20),\;(40,15)$
The feasible region is the triangular region with vertices $(2,72),\;(15,20),\;(40,15)$.