Find the largest positive integer n for which n 3 + 1 0 0 is divisible by n + 1 0 .
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
Our methods are more or less the same :-P
Log in to reply
I did the ques in mind
Can you explain the last step of your solution please. If n=890 then 8 9 0 9 0 0 will be in fraction and thus our whole answer will be in fraction.So n + 1 0 should be the greatest factor of 900 , then only are answer will be an integer(i.e greatest value of n=440) Please explain
Log in to reply
If n = 8 9 0 , n + 1 0 9 0 0 = 9 0 0 9 0 0 = 1 .
Log in to reply
Firstly it should be 10 not 1 and second if n =889 then it is 889+10=899 and 900 is not divisible by 899 and thus our answer will be fraction again.
Log in to reply
@Chirayu Bhardwaj – n = 8 9 0 and not 889.
Log in to reply
@Nihar Mahajan – It is an inequality that n ≤ 8 9 0 so n could be 889.
Log in to reply
@Chirayu Bhardwaj – The question asks for largest value of n .
Log in to reply
@Nihar Mahajan – Okay ! thank you .+1
Log in to reply
@Chirayu Bhardwaj – No problem :)
@Chirayu Bhardwaj – this question is not valid for n smaller than 890 . i think. correct me if i am wrong
Log in to reply
@Chirayu Bhardwaj – I confused inequality with maximum value , sorry for being silly :(
Same solution!!
Nice solution. But instead of division, you could have used remainder theorem.
I also did the same....
Let,
n 3 + 1 0 0 = ( n 2 + a n + b ) ( n + 1 0 ) + c = n 3 + n 2 ( 1 0 + a ) + n ( b + 1 0 a ) + 1 0 b + c ⎩ ⎪ ⎨ ⎪ ⎧ 1 0 + a b + 1 0 a c + 1 0 b = 0 ⇒ a = − 1 0 = 0 ⇒ b = 1 0 0 = 1 0 0 ⇒ c = − 9 0 0 g cd ( n 3 + 1 0 0 , n + 1 0 ) = g cd ( − 9 0 0 , n + 1 0 ) = g cd ( 9 0 0 , n + 1 0 ) Maximum value of n = 8 9 0
I believe you mean " + c " in the second step.
Nice solution have you solved my logical question named KILLING SEQUENCE?(available on my profile)
Problem Loading...
Note Loading...
Set Loading...
So we want to find largest integer n such that n + 1 0 n 3 + 1 0 0 is an integer,
n + 1 0 n 3 + 1 0 0 = n + 1 0 n 3 + 1 0 0 0 − 9 0 0 = n + 1 0 ( n + 1 0 ) ( n 2 − 1 0 n + 1 0 0 ) − 9 0 0 = n 2 − 1 0 n + 1 0 0 − n + 1 0 9 0 0
For the above expression to be an integer , the largest value of n is 8 9 0 .