Q6. Grids
MCQ · +3 / −1
One resident whose house is located at L, needs to visit the post office as well as the bank. What is the minimum distance (in m) he has to walk starting from his residence and returning to his residence after visiting both the post office and the bank?
- A) 3200
- B) 3000
- C) 2800
- D) 2700
Correct Answer
A) 3200
Step-by-step solution
📌 Core Concept
The walk is a closed loop L → P → B → L. Its minimum length is the sum of the three shortest legs between these points.
🔢 Step-by-Step Solution
1
Set up the grid distances. The columns are at 0, 150, 450 and 750 m (from , , ). The row gaps are , and . The diagonal is the hypotenuse of a 300-400 triangle, so . The diagonal is .
2
L to P. The route L-K-O-P gives . L-M-N-O-P gives , and L-K-J-I-P also gives . The shortest is 950.
3
P to B. The route P-I-G-B uses the diagonal and gives . P-I-H-A-B gives , and P-O-J-G-B gives . The shortest is 1050.
4
B to L. Every route has to cover 400 m down and 750 m across, and none of them can use a diagonal. For example, B-G-F-K-L gives , and B-C-D-E-L gives . The shortest is 1200.
5
Total: . Visiting B before P gives the same loop in reverse, so the total is the same.
Quick Check
The loop L-K-O-P-I-G-B-G-F-K-L is 3200 m. Its legs are 950, 1050 and 1200.
Correct Answer: A