I ran into a question on a practice test which said "What is the difference between -8 and -3? I am 13, and I am quite capable of subtracting negative numbers; I just did -8--3 to get my answer, making it -8+3, then making that -5. However, when I checked my answers, I was told that it was wrong, and the answer was 5.

When finding the difference between two numbers, do you subtract the bigger number from the smaller or vice versa?

Thank a lot!

  • 1
    $\begingroup$ Bigger - smaller. $\endgroup$
    – nabla
    Jan 3, 2016 at 22:46
  • 8
    $\begingroup$ "The difference between a and b" is ambiguous. It might mean $a-b$ or $b-a$. I suspect most people mean $|a-b|$, but I just try to avoid the phrase in practice. $\endgroup$
    – user137731
    Jan 3, 2016 at 22:46
  • $\begingroup$ Usually, the difference between $a$ anf $b$ denotes $\lvert a-b\rvert$. $\endgroup$
    – Bernard
    Jan 3, 2016 at 22:47
  • 4
    $\begingroup$ It is ambiguous, but if forced to choose, I would say first minus second. You might contact who wrote the test and ask them. Usually professionally written tests are quite careful to not be ambiguous $\endgroup$
    – Nate 8
    Jan 3, 2016 at 22:49
  • 4
    $\begingroup$ Rejoice that you know the difference between $a-b$ and $b-a$, that's a proper mathematical distinction . Take care in exams at your level that you understand what the examiner is asking (which may be different from your spot on precision). The game in exams is to get the marks. The game in maths is to get it correct. In exams, you play the examiner's game (as I explained to one of my daughters in a similar situation). $\endgroup$ Jan 3, 2016 at 22:57

2 Answers 2


I would read this as "what is the distance between these two numbers". The "distance" between two numbers is always non-negative.

  • $\begingroup$ @JMoravitz - thanks for the correction $\endgroup$
    – Mufasa
    Jan 3, 2016 at 23:30

The way I see this and apologies I am not expert, but:

1 -> 10 is the number line. 5 is where we want to be, the target number.

Variable + Target / 2 = Mean / Target = the degree of difference


10 + 5 / 5 / 2 = 1.5

5 + 5 / 5 / 2 = 1

1 + 5 / 5 / 2 = 0.6

Look for the Mean, add the Variable + Target / 2 = Mean / Target = the degree of difference between the Target and the variable.

Apologies if this is not what was intended. This was a good exercise for my interpretation of the same question.


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