Question 9
Arrange the numbers 1, 2, 3, 4, 5, 6 and 7 in a row such that none of the first number, the sum of the first two numbers, the sum of the first three numbers, and so on, up to the sum of all seven numbers, is divisible by 3. In how many ways can this be done?
Answer: ______ ways
Answer: ______ ways