Quant problems section (Extreme problem)

[Archi]

I’m unclear on why the answer can’t be D. Here’s my reasoning:

The total marks on the test are 120, and 90% of that is 108, meaning Ahmed lost less than 12 points. Assuming he lost 11 points, this could come from several combinations:
a) He could have gotten 4 questions wrong in section 3, losing 8 points, and 1 wrong in section 1, totaling 11 points from 5 errors.
b) Alternatively, he might have missed 3 in section 1, losing 9 points, plus 1 in section 3, losing 2 points, which also adds up to 11 points from 4 errors.

Shouldn’t the answer then be D? Why is it B? I’m not fully convinced by Greg’s explanation. Please help.

[cylverixxx]

@Archi

a) He could have gotten 4 questions wrong in section 3, losing 8 points, and 1 wrong in section 1, totaling 11 points from 5 errors.
b) Alternatively, he might have missed 3 in section 1, losing 9 points, plus 1 in section 3, losing 2 points, which also adds up to 11 points from 4 errors.

Add the scores manually and see for each case. By that i mean something like:

4 questions wrong in section 3 → 11 questions correct in section 3: Now you compute the score generated from this like: 11(2) - 8 + …

Is his score > 108?

[Archi]

yeah I calculated and the score is less than 108 so how do I go about solving this in the most time efficient way? What do you suggest?

[cylverixxx]

Hmm, a time efficient method would be to use Quantity B to aid you. Basically, the “best places” to make 4 mistakes would be in section 2 (bc least negative marking), and then you see what impact making 4 mistakes in section 2 has on the overall percentage (it happens to be = 90%). Then it makes logical sense that quantity A must be less than 4 to satisfy the “received a score above 90%”.

Btw whoops i ended up editing my previous answer instead of actually replying. Also, hmmm i have another maybe more “satisfactory” answer but it’s a big longer(?) than this so idk if you’re interested in that.