There are nine boxes arranged in a array as shown in Tables 1 and 2. Each box contains three sacks. Each sack has a certain number of coins, between 1 and 9, both inclusive.
The average number of coins per sack in the boxes are all distinct integers. The total number of coins in each row is the same. The total number of coins in each column is also the same.
Table 1
Table 1 gives information regarding the median of the numbers of coins in the three sacks in a box for some of the boxes.
| 1st column | 2nd column | 3rd column | |
|---|---|---|---|
| 1st Row | 9 | 6 | |
| 2nd Row | 2 | ||
| 3rd Row | 8 |
In Table 2 each box has a number which represents the number of sacks in that box having more than 5 coins. That number is followed by a * if the sacks in that box satisfy exactly one among the following three conditions, and it is followed by ** if two or more of these conditions are satisfied.
| 1st column | 2nd column | 3rd column | |
|---|---|---|---|
| 1st Row | 1** | 2* | 2* |
| 2nd Row | 1** | 0* | 3* |
| 3rd Row | 3* | 2** | 0** |
ii) The median of the numbers of coins in the three sacks is 1.
iii) The maximum among the numbers of coins in the three sacks in the box is 9. How many sacks have exactly one coin?
9
Step-by-Step Solution
Key idea: This is a Grid Matrix / Box Array reconstruction question, recognisable because there is a array of boxes, equal row totals, equal column totals, and distinct integer box averages. To count sacks with exactly one coin, we must first reconstruct the triples in all nine boxes.
Step 1: Determine the box averages.
Each box has 3 sacks, and each box average is an integer. Since the nine averages are distinct, they must be .
Their total is . Since row totals are equal, each row's average-sum is . The same holds for columns. Thus the averages form a semi-magic square with constant .
Step 2: Use the strongest clues to fix some triples.
Sort each box as .
Conditions:
i)
ii)
iii)
R1C2 has median 9 and label . Its triple is . Condition iii is true, and exactly one condition is true, so . The sum must be divisible by 3, forcing . So R1C2 is , average .
R2C1 has median 2 and label . Its triple is . Exactly one sack is greater than 5, so . At least two conditions are true. Since the median is not 1, conditions i and iii must be true. So R2C1 is , average .
R3C1 has median 8 and label . All three sacks are greater than 5, and exactly one condition is true. Therefore . The triple is , and the sum must be divisible by 3. The only valid is 7. So R3C1 is , average .
Step 3: Complete the magic square of averages.
Column 1 sum is 15. R1C1 + 4 + 8 = 15 R1C1 = 3.
Row 1 sum is 15. 3 + 7 + R1C3 = 15 R1C3 = 5.
The remaining averages for the grid are 1, 2, 6, 9.
Row 2: 4 + R2C2 + R2C3 = 15 R2C2 + R2C3 = 11.
The only pair from {1, 2, 6, 9} summing to 11 is 2 and 9.
Column 2: 7 + R2C2 + R3C2 = 15 R2C2 + R3C2 = 8.
If R2C2 = 9, R3C2 = -1 (impossible). So R2C2 = 2, R2C3 = 9.
Then R3C2 = 6.
Row 3: 8 + 6 + R3C3 = 15 R3C3 = 1.
The averages are:
3 7 5
4 2 9
8 6 1
Step 4: Reconstruct the remaining triples.
R1C1 (avg 3, 1**): 1 sack > 5. Conditions i, ii true .
R1C3 (avg 5, 2*, median 6): 2 sacks > 5. Condition i true .
R2C2 (avg 2, 0*): 0 sacks > 5. Condition i true .
R2C3 (avg 9, 3*): 3 sacks > 5. Condition iii true .
R3C2 (avg 6, 2**): 2 sacks > 5. Conditions i, iii true .
R3C3 (avg 1, 0**): 0 sacks > 5. Conditions i, ii true .
Step 5: Count sacks with exactly one coin.
Count the 1s in each triple:
R1C1: 2
R1C2: 0
R1C3: 1
R2C1: 1
R2C2: 1
R2C3: 0
R3C1: 0
R3C2: 1
R3C3: 3
Total = 2 + 0 + 1 + 1 + 1 + 0 + 0 + 1 + 3 = 9.
Answer: 9