Question 16 A student of class XII studying Mathematics comes across an incomplete question in a book. Maximise 𝑍=3𝑥+2𝑦+1 Subject to the constraints 𝑥≥0,𝑦≥0, 3𝑥+4𝑦≤12, He/ She notices the below shown graph for the said LPP problem, and finds that a constraint is missing in it: Help him/her choose the required constraint from the graph. The missing constraint is (A) 𝑥+2𝑦≤2 (B) 2𝑥+𝑦≥2 (C) 2𝑥+𝑦≤2 (D) 𝑥+2𝑦≥2Given
Maximise 𝑍=3𝑥+2𝑦+1 Subject to the constraints
𝑥≥0,𝑦≥0,
3𝑥+4𝑦≤12,
First, we plot 𝟑𝒙+𝟒𝒚=𝟏𝟐
Putting x = 0, y = 3. So, point is (0, 3)
Putting y = 0, x = 4. So, point is (4, 0)
Checking these two points in the graph
Now, the other line passes through (1, 0) and (0, 2)
Equation of that line is
(𝒚 − 𝟎)/(𝒙 − 𝟏)=(𝟐 − 𝟎)/(𝟎 − 𝟏)
𝑦/(𝑥 − 1)=2/(−1)
𝑦/(𝑥 − 1)=−2
y = –2 (x – 1)
y = –2x + 2
2x + y = 2
Now, it could be (B) 2𝑥+𝑦≥2 OR (C) 2𝑥+𝑦≤2
Since (2, 0) is in shaded region, it should satisfy the constraint
Putting (2, 0) in (B)
2(2) +0≥2
4≥2
This is true
Since the constraint is satisfied,
Hence, 2𝑥+𝑦≤2 is our constraint
So, the correct answer is (B)
Made by
Davneet Singh
Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 15 years. He provides courses for Maths, Science and Computer Science at Teachoo
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