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Ask HN: Fundamental Math Dilemma

1 点作者 imheretolearn大约 1 年前
Does 35 divided by 7 mean 7 groups of 5 or 5 groups of 7? Without any units, it means 5 groups of 7. This also makes sense when you consider modulus operator. 37 % 7 gives 2 meaning 5 groups of 7 with 2 remaining in the last group. However, if we cover 35 metres in 7 seconds it means we covered 5 metres in 1 second and there are 7 such seconds ie 7 groups of 5. Is there a way to reconcile these concepts or division can mean both depending on the context?

3 条评论

rawgabbit大约 1 年前
I admit I am behind the times of what is taught in today&#x27;s schools. Anyways, here are my thoughts.<p><i>Does 35 divided by 7 mean 7 groups of 5 or 5 groups of 7?</i> I define a group as a set. A set contains members. Moreover, a set is a logical container that I intend to manipulate. The phrase &quot;35 divided by 7&quot;, to me, implies there are 7 sets. It is the similar to divide the inheritance among 7 heirs.<p><i>37 % 7 gives 2 meaning 5 groups of 7 with 2 remaining in the last group.</i> Based on the definition above, there are 7 sets. The modulus is &quot;2&quot;; &quot;2&quot; is a not a set. If you evenly divide the inheritance among 7 heirs so each heir gets an equal share, then the remaining inheritance is the modulus.<p><i>However, if we cover 35 metres in 7 seconds it means we covered 5 metres in 1 second and there are 7 such seconds ie 7 groups of 5.</i> Here we are talking about a rate specifically velocity. Rates are not the same as sets.<p>Unless you are talking about abstract math, these concepts should tie into the real world. A set is a logical division of something. I have 35 apples that I want to evenly divide among 7 students (7 sets). Thus each student will get 5 apples (5 members). Because I am the world&#x27;s foremost glutton, I can devour 5 apples every second (rate).
zero-sharp大约 1 年前
We have 35 apples and we want to allocate, or divide, them evenly to 7 people. We are trying to create 7 groups from the 35. The &quot;group&quot; in this context is &quot;the number of apples per person&quot;. Notice that it&#x27;s a rate, a &quot;unit rate&quot;.<p>You can also say we found 5 groups of 7, but this phrasing seems to emphasize something different in the context of the original problem. If you say &quot;5 groups of 7&quot;, then the group is &quot;the number of people we need in order to allocate 5 apples evenly.&quot; This sounds confusing and there&#x27;s probably a better way to write it, but I think you get the point.<p>So, sure, 5x7 = 7x5. That&#x27;s a fact of arithmetic and, if we&#x27;re just talking about logic and numbers, we can be a little careless. But if you&#x27;re representing something with the numbers, it&#x27;s a little different.
x86x87大约 1 年前
&gt; This also makes sense when you consider modulus operator. 37 % 7 gives 2 meaning 5 groups of 7 with 2 remaining in the last group.<p>Where is this coming from? The modulus is just integer division with a remainder. If you use your theory of interpreting this you can do it both ways.<p>Division is taking something and spliting it in X parts. By definition: the act of separating something into parts or groups<p>So when you are divinding by X you are separating the initial quantity into X equal parts.<p>35&#x2F;7 means divide 35 in 7 equal parts.
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