not as simple as it looks

find the no of positive integral solutions of \left[ \frac{x}{900}\right]=\left[ \frac{x}{901}\right]

17 Answers

11
Mani Pal Singh ·

tarika bata diya

ab ginn lo apne aap[4]

1
Vivek ·

great work, both of you

1
gordo ·

im glad dat atleast someone bothered to end dis one...thanx celestine!!! ;-))

9
Celestine preetham ·

gordo thats the best approach

edit of gordos post

this as we are looking for positive values of p,

for r=K, we have K values of q so that r-q is positive,
ie 1 +2+......899 = 899*900/2

now when r=q ,p=0 means x=r is still valid

so in that case x can be 1 to 899

so final ans is 899*451 which is one less

all the others abv have considered x=o also as a solution thats the mistake

post is ended now !!!!

1
gordo ·

guyz why does every gud thread of this sort left to die incomplete??

1
gordo ·

say x=900p + r
and also x=901p + q
where 0<=r<900
and 0<=q<901

we have 900p +r= 901p +q
or p=(r-q)
now r belongs to [0,899]
and q belongs to [0,900]
as we are looking for positive values of p,
for r=K, we have K+1 values of q so that r-q is positive,
so the number of solutions can go up to
900+899+898+....+1=(900*901/2)
mite be completely wrong...

11
Mani Pal Singh ·

had hai
maine to aakhri digit tak bata di
please
now this is closed[4]

1
Vivek ·

the actual answer is 1 less than that,why????? any explanation?

Proof:

double a,c;int b;
int ctr=0;

for(b=1;b<=(900*901);b++)
{
a=(int) (b/900);
c=(int) (b/901);
if(a==c){
ctr++;
}
}
System.out.println("Ctr:"+ctr);

Output:
init:
deps-jar:
compile-single:
run-single:
Ctr:405449
BUILD SUCCESSFUL (total time: 0 seconds) --> lol

Did this to confirm as i had modified a past olympiad question

1
ith_power ·

1+2+...+899=450*899

11
Mani Pal Singh ·

r u sure ur question is complete??
please mention the interval

1
Vivek ·

yep, now do the counting

11
Mani Pal Singh ·

[339]

GOOD OBSERVATION ITH POWER
AMAZING
THEN

[1,899]
[902,1799]
[1803,2699]
[2704,3599]
[3605,4499].
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[45051,45989]
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[54062,54899]

[72081,72899]

[90101,90899]

[450501,450899]

[809999,809999]

last number to be multiplied by 900 is 899
in lhs we add the number with which we r multiplying
and in the rhs we a r multiplying with n-1 and subtractng 1

i hope this is the required solution[1]

1
ith_power ·

obviously the list will not count to infinity.
as you see the solutions you listed earlier, the range reduces by 1 each time.

1
Vivek ·

not infinity,but quite a large number( btwn 100000 and 1 million -)

11
Mani Pal Singh ·

CAN WE COUNT THEM ?????????

THE LIST EXTENDS UPTO INFINITY

SORRY IF AM ASKING A DUMB
BUT
THIS IS AN OBVIOUS QUESTION

11
Mani Pal Singh ·

[1,899]
[902,1799]
[1803,2699]
[2704,3599]

1
Vivek ·

positive integral solutions of x

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