This part is in a Children's math book, it teaches how to use cancellation in dividing. the sum is 270/18. 270 and 18 are both broken down to their prime factors, so it become 2x3x3x3x5/2x3x3, and the female character in the book suddenly sing "You are feeble and you know it"in the illustration nearby. What does the it mean in this context, why would she say that?


270/18 = 2x3x3x3x5/2x3x3 Now we can cancel. This means if any number on the top has a matching number on the bottom, We can cross them both out!

[Illustration] "You are feeble and you know it" (the female character sings this out, holding a scarf with both hands above her head)

We are just left with 3*5 on the top, that gives the answer 15, so 270/18 = 15

  • Are you sure it is "feeble"? Seems like an odd word for a kid's math book. – Lambie Sep 20 '20 at 15:59
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    British football ("soccer") fans, if their team has won a match, often call out "You're sh*t and you know it" to the fans of the opposing team. Maybe the girl is proclaiming victory over the arithmetic problem, and is being more polite than football fans? – Michael Harvey Sep 20 '20 at 16:02
  • Google reports no instances at all of the two sequences You are and You're ... feeble and you know it either in Google Books or the Internet at large. It's clearly modeled on the Baptist church / Football terrace chant If you're happy and you know it clap your hands (which itself leads to variants like you're shit and you know it for the latter), but I can't imagine what it's supposed to mean in the cited context. – FumbleFingers Sep 20 '20 at 16:07
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    I think the arithmetic problem is being proclaimed "feeble" because it has been defeated. – Michael Harvey Sep 20 '20 at 16:09
  • English uses You are [x] and you know it. incredibly frequently. However, feeble is rather odd here, as I said. We might say: You are very smart [well-dressed] and you know it. Or anything at all, really. He is so stupid and he knows it. This usage is a cliche. – Lambie Sep 20 '20 at 16:11

Holding a scarf and singing shows that this is meant to be a football (soccer) chant. Probably the suggestion is that by cancelling factors, the hard problem 270/18 has been reduced to an easy one.

Here is the point. Many students, when faced with 270 ÷ 18 will use long division. Long division is slow and it is easy to make mistakes, but children will toil through 18 into 2 doesn't go, carry the 2, 18 into 27 goes ... once, with remainder ... 27 - 18 = 9, bring down the 0 .... and so on.

The "factorise and cancel" method breaks down the problem into small steps and you don't need to do this hard work. For a 10 year old, that is something to cheer! And it is funny to insult the problem a bit. "You're feeble, and you know it!"

As with the rest of this book, unless you have the mind of a 10-year-old, it will seem rather childish.

  • I don't think I am an arithmetic wizard, but I can see just by looking that 270 is 30 x 9 and 18 is 2 x 9 so the answer is 30 / 2, or 15. – Michael Harvey Sep 20 '20 at 18:15
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    You may or may not be an arithmetic wizard... but you are not a ten year old child who finds maths "hard" can't remember all the "rules". You think about the problem and see the short cut. Children just don't do that. They have to be taught. And they are more likely to read a book that has some silly cartoons in it. Children are childish! Let's not judge them harshly for this. – James K Sep 20 '20 at 18:23

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