Question 1
Five boxes K, L, M, N, and O are stacked vertically (positions 1 to 5 from bottom to top).
Each box has a unique weight from the set: 15kg, 25kg, 35kg, 45kg, and 55kg.
Stacking rule: Heavier boxes must be placed below lighter boxes.
Conditions:
- Box O is at the bottom (position 1)
- Box K is at the top (position 5)
- Box N's weight is greater than Box M's weight, but less than 50kg
- The box immediately above Box M has weight less than 30kg
- Box L's weight is exactly 25kg
What is the weight of Box N?
Step-by-step Solution:
1. Apply stacking rule: Heavier below lighter
- So weights must decrease from bottom to top
- Position 1 (bottom) = heaviest
- Position 5 (top) = lightest
2. Fixed positions:
- Position 1 = Box O (given)
- Position 5 = Box K (given)
- Therefore: O is heaviest (55kg), K is lightest (15kg)
3. Box L's weight is exactly 25kg
- So L must be at position 4 (since 25kg is second lightest)
- Position 4 = L (25kg)
4. Remaining boxes: M and N for positions 2 and 3
- Remaining weights: 35kg and 45kg
5. Constraint: N > M (in weight)
- So N must be heavier than M
- Therefore: N at position 2 (45kg), M at position 3 (35kg)
6. Verify additional constraints:
- "Box N's weight is less than 50kg" → 45kg < 50kg ✓
- "Box immediately above M has weight < 30kg"
- M at position 3 → box above is position 4 = L (25kg) < 30kg ✓
7. Final stack (bottom to top):
- Position 1: O (55kg)
- Position 2: N (45kg)
- Position 3: M (35kg)
- Position 4: L (25kg)
- Position 5: K (15kg)
8. Answer: Box N weighs 45kg
Verification: All conditions satisfied ✓
1. Apply stacking rule: Heavier below lighter
- So weights must decrease from bottom to top
- Position 1 (bottom) = heaviest
- Position 5 (top) = lightest
2. Fixed positions:
- Position 1 = Box O (given)
- Position 5 = Box K (given)
- Therefore: O is heaviest (55kg), K is lightest (15kg)
3. Box L's weight is exactly 25kg
- So L must be at position 4 (since 25kg is second lightest)
- Position 4 = L (25kg)
4. Remaining boxes: M and N for positions 2 and 3
- Remaining weights: 35kg and 45kg
5. Constraint: N > M (in weight)
- So N must be heavier than M
- Therefore: N at position 2 (45kg), M at position 3 (35kg)
6. Verify additional constraints:
- "Box N's weight is less than 50kg" → 45kg < 50kg ✓
- "Box immediately above M has weight < 30kg"
- M at position 3 → box above is position 4 = L (25kg) < 30kg ✓
7. Final stack (bottom to top):
- Position 1: O (55kg)
- Position 2: N (45kg)
- Position 3: M (35kg)
- Position 4: L (25kg)
- Position 5: K (15kg)
8. Answer: Box N weighs 45kg
Verification: All conditions satisfied ✓