The do-while-loop is suitable for situations where the test value is input or calculated in the loop body, often leading to a compact solution. One aspect of the average problem complicates the do-while solution. When the user enters a -1 to end data input, the program increments count and updates sum before the loop ends. The program decrements count and increments sum below the loop, correcting the end-of-loop problem before calculating the average. The program also fails if the user enters a value < -1.