Which is larger...

Without calculating, which is greater?

\frac{361254001}{722508003} or \frac{361254002}{722508005}

If I remember correctly, this is one of the first things i learnt from Hall & Knight

Edit:

Hint: if A/B< C/D, what can you say about A+CB+D

26 Answers

11
sagnik sarkar ·

Sir,please tell whether my answer is correct or not?

62
Lokesh Verma ·

@fibonacci.. you are right.. there was a small typo..

:P

1
fibonacci ·

but how can we use the above fact as
725008003≠2n+1 where n=361254001

341
Hari Shankar ·

or if you consider f(n) = \frac{1}{2 + \frac{1}{n}}, its easy to see that it increases with n.

62
Lokesh Verma ·

good work :)

1
fibonacci ·

got it
a/b<c/d
ad<bc
adding ab to both sides
(a+c)/(b+d)>a/b
a=361254001 , b=725008003 , c=1 , d=2
the result follows

62
Lokesh Verma ·

you are so close fibonacci..

you have to identify a, b, c, and d :P

1
fibonacci ·

from nishant sir's hint
a/b<c/d
ad<bc
adding cd to both sides
(a+c)/(b+d)<c/d
how can we prove the inequality from this result

1
fibonacci ·

set 361254001=n and 725008004=x
assume n/(x-1) > (n+1) / (x+1)
or nx+n > nx+x-n-1
or 2n>x-1
which is a contradiction
so 361254001/725008003 < 361254002/725008005

62
Lokesh Verma ·

try a bit more :)

and see why this is relevant here ;)

I am sure you will be able to reason out this question yourself...

11
sagnik sarkar ·

Sir,plese solve the problem according to your hint.
abhi bhi hence proved nehi hua.

1
Bicchuram Aveek ·

Hence Proved ........ ;-)

Sir please keep posting such questions....these are really entertaining.

62
Lokesh Verma ·

The answer is correct and so is teh reasoning..

seee my hint for a general view on the same question :)

1
Bicchuram Aveek ·

which chapter, sir ?

11
sagnik sarkar ·

361254002/725008005>361254001/725008003

explanation:If we prove that;
361254002*725008003>361254001*725008005
then we are done.
now if both 725008003 and 725008005 were multiplied by 361254001 then 725008005* ".." would be greater than 725008003* ".." by 722508002(361254001*2).

Now,this is less than 725008003.
Thus,725008003* "..">725008005* ".."

1
Bicchuram Aveek ·

well eureka has hidden this answer.....but i can understand in which way he is trying to do it....i'll definitely try this out...

62
Lokesh Verma ·

@swastika... the problem with calculator is that the accuracy is lower than what we want for this problem ;)

@eureka.. yes it is correct

@Aveek.. I dont see any logic

1
Bicchuram Aveek ·

dunno.......i want a simpler logic

24
eureka123 ·

@sir
I would love to see the simpler logic.[1][1]

but this method is fine naa?

3
Swastika dutta ·

Sir, is the second one greater !! It is 361254002 parts out of 725008005 .
But with calculator both the values are coming to be 0.49827588.
COULDN'T Understand!!

1
Bicchuram Aveek ·

made some changes

62
Lokesh Verma ·

@aveek: do you think your first assertion is correct?
@Eureka..: there is a far simpler logic...

24
eureka123 ·

easy...
361254002725008005=361254001+1725008003+2

361254001725008003-361254001+1725008003+2

=361254001.(725008003+2)-(361254001+1)725008003(725008003)(725008003+2)

=361254001.2-361254001.725008003(725008003)(725008003+2)

=361254001(-......)(725008003)(725008003+2)<0

=>361254001725008003-361254001+1725008003+2<0

=>361254001725008003-361254002725008005<0

=>361254001725008003 <361254002725008005

I dont know whether I am allowed to post the answer..so I am hiding it[1]

1
Bicchuram Aveek ·

I think 361254002725008005 will be greater as

361254001725008003 <361254002725008004

and

361254002725008004 >361254002725008005 .........right ??? :-(

62
Lokesh Verma ·

no they are not... think again! or else use the calculator to check ;)

3
Swastika dutta ·

Sir, both the values should be equal.

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