编写程序，运用随机函数rand()生成500道1000以内加法运算题，每一行排列5题，存入文本文件中。

编写这样的程序，你可以使用一种通用的编程语言如Python。这里是一个简单的示例，它将使用random库来生成题目并将其写入文本文件：

import random

# 设置题目范围
min_num = 1
max_num = 1000

# 定义每行的题目数量
questions_per_row = 5

# 创建一个空列表用于存储题目
rows_of_questions = []

for _ in range(500):  # 循环生成500道题目
    row = []
    for _ in range(questions_per_row):
        a, b = random.randint(min_num, max_num), random.randint(min_num, max_num)
        problem = f"{a} + {b}"
        solution = a + b
        row.append((problem, solution))  # 存储问题和答案对
    rows_of_questions.append(row)

# 将所有题目写入文本文件
with open("math_problems.txt", "w") as file:
    for i, row in enumerate(rows_of_questions):
        file.write(f"Row {i+1}:")
        for j, (question, _) in enumerate(row):
            file.write(f"\n{j+1}. {question}")
        file.write("\n\n")