В каждой клетке таблицы 4 × 5 стоит натуральное чи...

Created on: November 5, 2025

Answered using GPT-5 Thinking by Chat01

Question

В каждой клетке таблицы 4 × 5 стоит натуральное число. При этом все числа различны, но суммы во всех строках одинаковы и во всех столбцах тоже одинаковы. Какова минимально возможная сумма чисел в таблице?

Python

python
import itertools nums = list(range(1,20)) + [30] S = sum(nums) S 220

Python

python
nums = list(range(1,20)) + [30] sols = [] # find partitions into 5 groups of size 4 summing to 44 # This is large; use backtracking nums_set = set(nums) groups = [] nums_sorted = sorted(nums) count = 0 def search(available, start=0, groups=[]): if not available: yield groups[:] return # choose smallest remaining element to reduce symmetry a = min(available) # find 3 others b,c,d such that sum=44 rest = sorted([x for x in available if x!=a]) # Use combinations of 3 from rest for b,c,d in itertools.combinations(rest, 3): if a + b + c + [(1, 2, 11, 30), (3, 4, 18, 19), (5, 6, 16, 17), (7, 8, 14, 15), (9, 10, 12, 13)]

Python

python
groups = [ (1,2,11,30), (3,4,18,19), (5,6,16,17), (7,8,14,15), (9,10,12,13), ] import itertools # Represent assignment by, for each column, a permutation of indices 0..3 for rows # But we can think rows labeled 0..3. We'll generate row vectors by choosing for each column an index for row0, # etc and check if there exists alignment for all rows simultaneously. Equivalent to choose matrices of permutations. # We can brute force by backtracking across columns selecting a permutation for each column and tracking row sums. target_row_sum = 55 def backtrack(col, row_sums, perms): if col == len(groups): if all(rs == target_row_sum for rs in row_sums): yield perms[:] return g = groups[col] # Try all permutations of group g assigned to 4 rows for perm in itertools.permutations(g, 4): # prune by partial sums: any row sum exceed target? ok = True for r in range(4): if row_sums[r] + perm[r] > target_row_sum: ok = False break if not ok: continue # additional pruning: at last column, the needed value must equal remaining difference for each row # but that's automatic; skip row_sums2 = tuple(row_sums[r]+perm[r] for r in range(4)) perms.append(perm) yield from backtrack(col+1, row_sums2, perms) perms.pop() solutions = list(backtrack(0, (0,0,0,0), [])) len(solutions) 72

Python

python
solutions[0] [(1, 2, 11, 30), (18, 19, 3, 4), (16, 6, 17, 5), (8, 15, 14, 7), (12, 13, 10, 9)]

Python

python
perm = solutions[0] row_sums = [sum(perm[c][r] for c in range(5)) for r in range(4)] col_sums = [sum(perm[c]) for c in range(5)] row_sums, col_sums ([55, 55, 55, 55], [44, 44, 44, 44, 44])

Thought

Constructing the 4x5 table

The minimal possible sum will be 220. We need to show that this is the smallest solution (it must be a multiple of 20 and at least 210). I'll present a clear explanation and table proving that the sum of 220 is achievable, with 55 per row and 44 per column, ensuring distinct natural numbers in the solution matrix.

Constructing the 4x5 Table

Here's the matrix we derived:

Row 1: 1, 18, 16, 8, 12 (sum = 55)
Row 2: 2, 19, 6, 15, 13 (sum = 55)
Row 3: 11, 3, 17, 14, 10 (sum = 55)
Row 4: 30, 4, 5, 7, 9 (sum = 55)

Since the column and row sums are directly aligned, and all numbers are distinct, the minimal sum S=220S = 220 is verified. The lower bound was 210, but it must be divisible by 20, hence it starts at 220.

Thought for 2m 45s

Answer

Минимальная сумма равна 220.

Почему:

  • Пусть сумма в каждой из 4 строк равна RR, а в каждом из 5 столбцов — CC. Тогда общая сумма S=4R=5CS=4R=5C, т.е. SS кратна 20.
  • При этом числа попарно различны и натуральны, значит S1+2++20=210S\ge 1+2+\dots+20=210. Ближайшее к 210 кратное 20 — это 220, значит S220S\ge 220.

Осталось показать достижимость S=220S=220. Возьмём набор {1,2,,19,30}\{1,2,\dots,19,30\} (это сумма 220) и расположим так:

1181681221961513113171410304579\begin{array}{ccccc} 1 & 18 & 16 & 8 & 12\\ 2 & 19 & 6 & 15 & 13\\ 11& 3 & 17 & 14 & 10\\ 30& 4 & 5 & 7 & 9 \end{array}

Проверка: суммы по строкам =55=55, по столбцам =44=44, все числа различны. Следовательно, минимально возможная общая сумма — 220.

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