You need to use a loop to solve a problem dealing with 1D arrays when the problem requires me to consider each individual point in the array separately in order to process a change or function.
For example, if the problem asks me to perform a mathematical operation on each individual value in the array, I would need to use a loop in order to process each value independently. This is because a loop will iterate over each point in the array and provide each individual value as the loop parameter, which I can then utilize to execute the appropriate operations.