The Official CAT 2007 Quant Thread

[Aarav]

Originally Posted by the.bombardier

infinity is defined as a very large no..there is no specific representation of infinity.
that is when i take infinity - infinity,i can say one infinity is much larger than the other one..so infinity - infinity is not a definite no.

A very large number is still a large number and not infinity.
Seems you people are thinking in terms of subtracting billions from trillions and still achieving trillions which is infinity/or some crap according to you, but not to me.

[krsh.vik]

Originally Posted by chat.sun

So, u say even the option 3 is incorrect? Whtever it be, 'm sticking to my option (5). It has more than 1 answer

no no .. i say that option 3 is correct

[tatimatla]

Originally Posted by Aarav

Ok ... donning my old hat just for 1 question

Which among the following is/are incorrect?

1) (Infinity - Infinity) is a definite number
2) V4 takes exactly 1 value
3) -1 is a complex number
4) (Infinity + Infinity) = Infinity
5) more than 1 of the above

Aarav bhai...hatsoff to u...good to see such a simple (ahem) question generate such a great interest among the junta
here is my take:
1) NO -> using = sign for infinity is wrong. Phull ishtop.
2) Yes...the defenition of sqrt is that it's domain and range are non-negative real Nos.
3) Yes...Complex Numbers is the superset of Real Numbers.
4)NO -> reason stated in 1)
5) Yes

[Aarav]

Vineet, I have to leave for a class now. Do one thing, put this question on Art of Problem Solving and see what foreign junta has to say on this.
Put a link to your question here so that we can trace that.

My best learning here has been when I have been proven wrong

Ya ... thanks tatimatla ... an innocuous questions perhaps, but I knew what I was doing.

[vineet.nitd]

Originally Posted by Aarav

(4) I have no doubts that the use of = operator with infinity is wrong. An expression approaches a large value which can not be represented with a number, and if it can be represented with a number then put = operator.
Ever seen a lim problem where x = infinity is used? It's x-> Infinity.

(1) Where do you think the concept of Infinity originate from? I don't know what Infinity*Infinity - Infinity is but Infinity - Infinity is a definite number. lim (1/x - 1/x^2) as x->0 is not at atomic level ... I can break lim (1/x^2) as x->0 to lim(1/x)*lim(1/x) as x->0

Give me an example to disprove Infinity - Infinity is not a definite number and not Infinity - (infinity)^4 as with your example.

4> we say tends to infinity at the point where we wish to calculate limit as we wana see when we approach from +ve nd -ve sides ..but not for the result ..result will always be equated to infinity .If that were not the case ..we also say limit tend to 0 meaning approaching to a definite value from both sides of 0 , then y dont we have 0 - 0 -> 0 rather we have 0-0 =0


1>but infinity ^4 is also infinity .


Its not just a number ...rather an extension on number line

You may also say that cotx is not at its atomic level and can be expresed in terms of x and then u can have a expression with so many series terms replaced by infinity but the fact reamins ..it again wil calculate down to infinity .

Quoting from Wikepedia "Infinity comes from the Latin infinitas or "unboundedness." It refers to several distinct concepts (usually linked to the idea of "without end" or "bigger than the biggest thing you can think of") "

[siddhesh_j]

My answer is Option 1 ... Option 4 is correct coz Infinity + infinity is indeterminate and can be represented by infinity as well

[vineet.nitd]

Originally Posted by Aarav

Vineet, I have to leave for a class now. Do one thing, put this question on Art of Problem Solving and see what foreign junta has to say on this.
Put a link to your question here so that we can trace that.

My best learning here has been when I have been proven wrong

Ya ... thanks tatimatla ... an innocuous questions perhaps, but I knew what I was doing.

Yeah sure aarav ..Healthy discussion ..Thats wot we must expect here on a regular basis

Art of Problem Solving Forum

Here is the link where i ve posted the querry ..Wait nd watch ..

[chat.sun]

Well.. offtrack for the above question.. me stuck in another prob.. Can someone help me with this out here??

Q) Least number multiplied to 100! to make it perfectly divisible by 3^50 ???

[krsh.vik]

Originally Posted by chat.sun

Well.. offtrack for the above question.. me stuck in another prob.. Can someone help me with this out here??

Q) Least number multiplied to 100! to make it perfectly divisible by 3^50 ???

It is 3^2
3 | 100
3 | 33 - 1
3 | 11 - 0
3 | 3 - 2
3 | 1 - 0
hence 100! is divisible by 3^48
hence 9 is the ans

[chat.sun]

Originally Posted by krsh.vik

It is 3^2
3 | 100
3 | 33 - 1
3 | 11 - 0
3 | 3 - 2
3 | 1 - 0
hence 100! is divisible by 3^48
hence 9 is the ans

Hey krsh, can u plz explain me wht u were doin? U r finding the factors of 100 and how did u conclude tht 100! is div by 3^48??