The correct answer is: C. 9 + 6 + 4 = 19
We see a relatively simple question here.
Since this test is timed, we want to make sure that even on easier questions, we work in a systematic and as efficient way as possible.
Because we are dealing with three boxes that need to be filled, we’ll divide the solution into two parts:
First step: Choose the first number thoughtfully to place in the first box. We select this number based on the information we are given. Here, we see that the result is relatively high considering that only addition is involved. This suggests we should start with a high number. We’ll therefore try placing the highest number available to us, which is 9.
Second step: Now we move on to determine the numbers for the remaining boxes. The total we need to reach is 19, so after placing 9, we are left with 19 − 9 = 10.
Now we can think of all pairs of numbers that add up to 10. Note that there are two combinations you cannot use: 5 and 5, and 1 and 9, since you cannot repeat the same digit twice.
Wrong Answer A: 9 + 5 + 5 = 19 Result is correct but repeats the digit 5 twice - the most natural trap on an addition question where candidates find the sum first and ignore the no-repeat rule.
Wrong Answer B: 8 + 7 + 3 = 19 Feels like a clean answer but 8 + 7 + 3 = 18, not 19. A believable off-by-one error made under time pressure.
Wrong Answer D: 9 + 1 + 9 = 19 Repeats 9 and also reuses a digit already placed in the first box - a double violation that candidates miss when they are rushing through the easier early rounds.