# Math forum

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lisa
 #1 Posted : Tuesday, April 12, 2011 3:04:19 PM

Joined: 3/16/2011
Posts: 33

At McDonalds you can order Chicken McNuggets in boxes of 6, 9, and 20. What is the largest number such that you can not order any combination of the above to achieve exactly the number you want?

mohit
 #2 Posted : Tuesday, April 12, 2011 4:10:25 PM

Groups: Registered Users

Joined: 3/16/2011
Posts: 44

.any multiple of 3 which is greater than or equal to 6 is possible by combining 9 and 6...as 6 will take care of all the even multiples of 3 and the combination of 9 and 6 will take care of every odd multiple of 3...now in case u order a number which leaves 2 as the remainder on dividing 3 then it will be served with the help of number 20 box..as 20 = 18+2 so when u subtract 20 from tht number then it will give u a number divisible by 3 for eg take 26 it will give u 2 as the remainder on dividing 3 ..now first order 20 number box u r left with 6 which is easily orderable...now we will jump on the case when u get the remainder as 1 on dividing the number by 3...in tht case we will use 2 20 number boxes...now when we subtract 40 from any number with remainder 1 we will surely b left with a number which is a multiple of 3...so at last we came to a conclusion tht any number greater then 40 is orderable provided tht on subtracting 20 or 40 frm it, it turned out to be a multiple of 3 greater then 6 in other words we are sure tht any number greater then 46 is orderable...now we will check for numbers less then 46...45 and 44 are easily orderable as they give 0 and 2 as remainder but wht abt 43?...it will give 1 as a remainder and on subtracting 40 it will give 3 which is not aderable...so 43 is the answer..

 #3 Posted : Wednesday, April 13, 2011 7:30:47 AM
Rank: Member

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Joined: 3/21/2011
Posts: 20

osome, Mohit.. :)

mohit
 #4 Posted : Friday, April 15, 2011 3:13:07 PM

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Joined: 3/16/2011
Posts: 44

tt4lif
 #5 Posted : Tuesday, May 31, 2011 10:38:45 PM
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Joined: 5/31/2011
Posts: 8

the answer is : ( copying and pasting what mohit says cause i believe he rite even though i ddnt even read his answer cuzz i just beleive he smart like that.! see mohit i have faith and confidence in you unlike some ppl:) 25\$ on MOHIT!!!!!!!!!!!!!!!!!!!!!!!!!

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