Q13. Arrangements
MCQ · +3 / −1
In how many different ways can the items be arranged on the shelves?
- A) 4
- B) 1
- C) 2
- D) 8
Correct Answer
D) 8
Step-by-step solution
📌 Core Concept
Place the clusters (savouries, biscuits, candies) using the empty-shelf rules, then count the orderings the clues leave open.
🔢 Step-by-Step Solution
1
Clue 4 puts K in shelf 16. Savouries come after all biscuits and candies, so K is a savoury. D, E, F are consecutive and increasing, so the savouries are D, E, F, K in shelves 13 to 16.
2
Shelf 12 must be empty, because different types need a gap. That leaves 8 items (5 biscuits, 3 candies) in shelves 1 to 11, and 16 - 12 = 4 shelves are empty in total.
3
Clue 6 says C is a candy preceded by two empty shelves, so C starts the candy cluster. Clue 7 says L is preceded by exactly one empty shelf, so L starts a cluster. L cannot start the candy cluster (C does) or the savoury cluster (D does), so L starts the biscuit cluster.
4
Clue 5 makes J the same type as L, so J is a biscuit. Clues 1 and 2 add A, B and I, J, so the biscuits are L, A, B, I, J. The candies are C, G, H, and H is a candy because it differs from L's type. The savoury group is D, E, F, K.
5
With 4 empty shelves in total, only two layouts work:
Layout P: empties at 1, 2, then candies at 3 to 5, empty 6, biscuits at 7 to 11, empty 12.
Layout Q: empty 1, biscuits at 2 to 6, empties 7 and 8, candies at 9 to 11, empty 12.
6
In each layout the biscuit order is forced as L, A, B, then I and J in either order. That gives 2 ways.
7
C is first among the candies, and G and H can swap. That gives 2 ways.
8
Each layout gives arrangements, so the total is .
Quick Check
The two layouts are the only ones with exactly 4 empty shelves that satisfy clues 6 and 7, so .
Correct Answer: D