Concept:Since
z=5x+10y=5(x+2y), maximizing
z is equivalent to maximizing
x+2y, which is directly limited by the constraint
x+2y≤10.
Explanation:The constraint
x+2y≤10 gives the maximum possible value of
x+2y as
10.
Hence, the maximum value of
z is
z=5(10)=50.
This maximum is achieved only when
x+2y=10.
So we find the feasible portion of the line
x+2y=10.
On the
y-axis,
x=0, so
2y=10, giving
y=5. This gives the point
(0,5).
Now intersect with
3x+y=12.
From
x+2y=10, we get
x=10−2y.
Substitute into
3x+y=12:
3(10−2y)+y=12⇒30−5y=12⇒y=518.
Then
x=10−2(518)=514.
The other point is
(514,518).
Every point on the segment joining these two points satisfies
x+2y=10 and lies in the feasible region, so the maximum value of
z is attained along the whole segment.
Answer:The maximum value occurs at every point on the line segment joining
(0,5) and
(514,518), i.e., Option D.