Math
Received answer to the following question from Jishka. (2469)
Would you please explain the steps you used to get the answer 2469. I must show work.
Thank you
Using the 9 digits, 1, 2, 3, 4, 5, 6,7, 8 and 9 you can arrange four different digits to form a fourdigit number that is NOT divisible by 7. The digits 1238 cannot be arranged to create a fourdigit number that is divisible by 7. The digits 1389 also cannot be arranged to form a fourdigit number that is divisible by 7. Find one additional set (not 1238 or 1389) of four different digits that is not divisible by 7. Provide the digits to form the smallest four digit value.

I could think of no easy way to determine the answer. I'd be interested to know what the teacher says as far as finding the solution quickly. I think that questions like this are a waste of time, because there's no real mathematical insight to be gained. It's just a matter of searching for something in a long list.
To that end, I wrote a small perl program that just tried all the 4digit numbers. That was the only solution found.
Now, if they had wanted divisibility by 3 or 9, then you could use the casting out nines, which says that if the sum of the digits is divisible by 9, so is the number. Even that gives little help in reducing the list.
Unfortunately, casting out sevens requires factoring the number, so it doesn't help much. If any of the factors is divisible, then so is the number. (duh)
So, another way might be to check all numbers that contain only prime factors not including 7: 2,3,5,11,13,... but that's also tedious.posted by Steve
Respond to this Question
Similar Questions

Math Help Please
Can you Please explain the answer that I received of 2469? It is the correct answer but I do not understand how to show the work. Thank you *************************************** Using the 9 digits, 1, 2, 3, 4, 5, 6,7, 8 and 9 
Math Help Please
Would you please explain the steps you used to get the answer 2469. Thank you Using the 9 digits, 1, 2, 3, 4, 5, 6,7, 8 and 9 you can arrange four different digits to form a fourdigit number that is NOT divisible by 7. The digits 
Math 7 A
Note: For questions 5 and 6, remember to show all of the steps that you use to solve the problem. Be sure to use the text box where the question mark (?) first appears to show your mathematical work. You can use the comments field 
Math (Help!)
Note: Remember to show all of the steps that you use to solve the problem. Be sure to use the text box where the question mark (?) first appears to show your mathematical work. you can use the comments field to explain your work. 
Math
I help solving these out can someone work through them with me???? 19. WorkPad Note: In questions 1921, remember to show all of the steps that you use to solve the problem. Be sure to use the text box where the question mark (?) 
Unit 1 lesson 7 math
1. if MNO is = to QSR witch of the following is true? 2.The triangles shown are congruent. Find the measure of P 3.Which congruence statement says the same thing as ABC = DFE 4.Note: Remember to show all of the steps that you use 
Simplfing Fractions
Three problems I need to know if I am correct or not if not I will place how I got the answer and maybe some one can show me where I messing up aT Simplify 1+2/3 over top 2+1/2 My answer was 2/3 to me it does not seem right If I 
Math
Hello, I need a little assistance with showing my work on this question. The equation is 4 7/8 x 2/3. I have to explain how this person is wrong then show the work the correct way. Okay so the person's work is written as, "4 7/8 
Math "Need Help Asap"!
19. WorkPad Note: In questions 1921, remember to show all of the steps that you use to solve the problem. Be sure to use the text box where the question mark (?) first appears to show your mathematical work. You can use the 
math/ algebra 1
can someone please help me explain how they got this answer and can someone please show me the steps into solving this question? Q: Four more than the quotient of a number and three is at least nine.