Math Is Fun Forum

lorynjane

Member

Registered: 2011-02-27

Posts: 13

Could you please explain this to me as i dont get the question?

Just before Jonathan and Jim step out for a space walk, Jean-Luc decides to give them a challenge:
"I'm thinking of a prime number less than 10000. The product of its digits is zero and its first digit is equal to the sum of the other digits."
Jonathan replies that this is insufficient information to work out the number.
Jean-Luc then adds " Reversing the digit gives you a number which is divisible exactly by three prime factors, two of which are 19 and 29."
Jim states that this is now enough information.
What number is Jean-Luc thinking of?

(Ive been working on this question all day and came on this website when my mam suggested that i should look for help on the internet, I think that the answer must have a 0 in it somewhere as the product of the digits has to be zero but thats as far as i know? )

Bob

Administrator

Registered: 2010-06-20

Posts: 10,640

Re: Could you please explain this to me as i dont get the question?

hi lorynjane,

Wow! That's some problem.  I had to search the internet for a list of primes, eliminate those without a zero in them (well done for spotting this!), then reverse the digits and test for divisiblity by 19 and 29.

I have found a prime.  But I think I shouldn't just tell you it, so I'm sitting on my answer for the moment to see if there's a sensible way you can find it yourself.

Meanwhile, concentrate on the other questions because these are ones you can do, I'm sure.  When you have those sorted post back your answers.  Then we'll think about the primes question.

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

lorynjane

Member

Registered: 2011-02-27

Posts: 13

Re: Could you please explain this to me as i dont get the question?

ive done the other questions now and its just this one that i dont understand??

Bob

Administrator

Registered: 2010-06-20

Posts: 10,640

Re: Could you please explain this to me as i dont get the question?

hi,

Have another look at the common multiples question.  You have got one number. That's good but can you give other common multiples?

Then there's the astronauts and mother's age question.  Have you said how old she is?

Cubes problem.  What have you got as an answer to this.  Still 5?

If I was your teacher, I don't think I'd be happy with just 5 as an answer.  Anyone could pluck a number out of the air and say it.  Seven, twenty one, one hundred and five ....

Have you got sketches for your answers to justify that five is right?  How do you know there are no more?

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

Bob

Administrator

Registered: 2010-06-20

Posts: 10,640

Re: Could you please explain this to me as i dont get the question?

hi everybody and anybody,

This makes an interesting problem.  Maybe have a go.  I think it's a unique solution. 

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

gAr

Member

Registered: 2011-01-09

Posts: 3,482

Re: Could you please explain this to me as i dont get the question?

Hi all,

Using a computer, I got 2011.
Is there any elegant method?

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"Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense"  - Buddha?

"Data! Data! Data!" he cried impatiently. "I can't make bricks without clay."