input: Write a function to calculate the average of five numbers entered by a user.
  
  assert calculate_average([10, 20, 30, 40, 50])==30
  assert calculate_average([5, 10, 15, 20, 25])==15
  assert calculate_average([2, 4, 6, 8, 10])==6
  assert calculate_average([1, 2, 3, 4, 5])==3
  assert calculate_average([100, 200, 300, 400, 500])==300
output: def calculate_average(numbers):
      return sum(numbers) / len(numbers)