(no subject)

[tinyjo]

So, if we're going to buy expensive schemes to teach children maths, can the providers please make sure that the activities make sense and aren't, you know, wrong or anything.

Say the number: four thousand, seven hundred and eighty-three. Ask children in their groups to write this in figures. Write it on the board to check: 4783. What is the lowest number you can add so that all four digits change? Allow 3 or 4 minutes to try this, then take feedback. (1111 is the lowest number that can be added so that all four digits change, making 5894.) Will this always be the lowest number? Can you find a 4-digit number where all four digits can be changed by adding a lower number? Ask children to explore this, starting by finding different types of number (e.g. multiples of 10 or 100) where a lower number can be added. Ask them to write some general rules (e.g. if the number ends in 9, then the lowest number that can be added to make all four digits change is 1101.)

Just.... No, don't do that! I can't even think of an interpretation that might make that make sense.

Comments

but...

[jinty]

that question is expecting an answer where all the numerals increase, whereas you could easily get a new number where all the digits change without all increasing...

[celestialweasel.livejournal.com]

This is trying to be about carrying I think e.g. If you have 9999 then you add 1 and all 4 digits change. So I think it makes sense but is awfully written. It reads more like some Martin Gardneresque mathematical puzzle than anything.

[phlebas.livejournal.com]

It almost works - if the number ends in 9 and none of the other digits is a 9 then 1101 is indeed the lowest number you can add to change all four.
I'm not sure what they're talking about with the multiples of 10 and 100 though.

[cleanskies.livejournal.com]

Is there a column in the Guardian you can send this in to? Or Bad Science? Please send it somewhere, because this is nonsense.

[truecatachresis.livejournal.com]

Contrary to other responders here, I suspect the question is asking for the smallest number added where all the digits change and remain different to each other.

Still, it's a really crap exercise that doesn't appear to be useful at teaching anything.

[tortipede.livejournal.com]

Thinking this through more, and re-reading everybody's comments, I think what they're trying to do is to move children from a mathematical worldview that doesn't take account of carrying, where 1111 would be the only possible answer, to one that does — using, as phlebas said, a sort of vaguely scientific-ish experimentation approach. They're meant to start off with 1111 and arrive at 217, discovering the Joy of Carrying for themselves along the way — at least, that's how I read the business about 9 and 1101. But by implying that 1111 is the correct answer rather than a good starting point, they've neither said what they really meant nor meant what they said. Yesno?

[bluedevi.livejournal.com]

It's surprisingly common, that. The Computing and ICT A-level papers are full of logical flaws. I have a student who's been programming for years and if he thinks about the problems logically, rather than in the sort of vague sloppy pseudocode idiom of the textbooks which does not exist except in the bubble of A-level computing, he gets them wrong.

But, I thought, surely the country is full of people who would delight in coming up with good puzzles for exam papers. I know a good few who would do brilliantly at that. But I imagine they're all programming for good money, not working at exam boards.