I was doing an exam using Moodle 2.8.4 version; some questions (of the calculated type) were scored wrongly although the answer is the same as that calculated by MOODLE quiz engine. Here is an example:
The student answer: 3.6 & the MOODLE calculated answer: 3.6; However; the answer is considered wrong.
The correct answer is not 3.6. It will be 3.6... or 3.5..... When that is displayed to 2 significant figures, it looks like 3.6, but that is not the exact numerical value, and computers do exactly what you tell them.
You probably need to set a 'tolerance' for the answer, so the question knows that 3.6 is close enough to the right answer.
Thanks a lot.