First, going from 475 to 605 is excellent progress. You have already moved your score significantly.
Regarding the Q79 with only three incorrect answers, I would not focus too much on the raw number of questions you missed.
The GMAT is computer-adaptive, and your Quant score is based on the overall pattern of your performance, not simply the number of questions you answered correctly or incorrectly. Also, getting the first question wrong does not carry some special scoring penalty.
So, three incorrect answers can absolutely result in a Q79. The specific questions you miss and the overall pattern of your performance matter.
The other thing that caught my attention is that you finished Quant with a lot of time remaining.
Having some time available for Review & Edit is a good thing. However, if you are consistently finishing with a substantial amount of extra time while scoring Q79, I would look carefully at whether you are moving too quickly through certain questions on your first pass.
You do not receive any scoring benefit for answering questions faster. So, on questions where another 30 or 45 seconds could materially increase your probability of getting the answer correct, that may be time worth investing. At the same time, you certainly do not want to overinvest in difficult questions just for the sake of using more time.
The goal is not to use every second. The goal is to allocate your time where it has the greatest chance of producing additional correct answers.
More broadly, your Q79, V82, and DI79 tell me that this is not really a “fix Quant and you are done” situation. To move from 605 to 655+, I would continue strengthening all three sections.
Go through your performance data carefully and identify:
Which Quant topics are producing the misses
Which Verbal question types are inconsistent
Which DI question types are costing you points
Whether each mistake is caused by a knowledge gap, a strategy issue, an execution error, or timing
Then attack those weaknesses individually.
I would also resist the temptation to keep taking mock after mock. Mocks are useful for measuring your current level, but they are much less efficient for actually raising it. Spend most of your time between mocks building the specific knowledge, skills, and strategies that your 605 score is telling you are still missing.
You have already gained 130 points. Now the work becomes more targeted.
If you post the detailed topic breakdown from this mock, I’d be happy to take a look at where I think the next 50+ points are most likely to come from.
Good luck!
Scott
Target Test Prep