GMAT Math

bsingh3 wrote:1) how many real roots does 4X^6 + 3X^4+20=0 has?

None - 4x^6 and 3x^4 cannot be negative, so there will be no value of x for which 4x^6 + 3x^4 = -20

bsingh3 wrote: 2) y=ax^2+bx+c=0, where does it corss the x axis?

This is just asking if you know the quadratic formula, something I've never seen tested in a real GMAT question. Not worth worrying about, but the answer will be (-b + root(b^2 - 4ac))/(2a) and (-b - root(b^2 - 4ac))/(2a).

bsingh3 wrote: 3) DS question:
whats the 100th digit in x ?
a) when reduced to 100th place then its 2600
b) x>2687

I don't understand the language - you won't ever see a phrase like 'when reduced to 100th place' on the GMAT, since it's meaningless.

bsingh3 wrote:
4)remainder is 1 when x+y is divided by 5, remiander is 2 when y+z is divided by 5, and remainder is 3 when z+x is divided by 5, then what is the remainder when x+y+z is divided by 5?

Quite a few ways to do this - you could just find numbers for x, y and z, for example (x = 1, y = 0, z = 2 work, say).

Or, you could do this abstractly:

x+y = 5a + 1
y+z = 5b + 2
x+z = 5c + 3

Adding the equations, we have 2x+2y+2z = 5(a+b+c) + 6. Since the left side is divisible by 2, the right side must be, so a+b+c must be some even number 2k, and when we divide by 2 on both sides, we have:

x+y+z = 5k + 3

So the remainder is 3 when x+y+z is divided by 5.

bsingh3 wrote:
5) The sum of scor is 1680 for 5 people and the score is 79 which is 1.25 standard deviation, what is the score if its 0.5 SD?

I have no idea what this question means. You won't see language like this on the GMAT.

bsingh3 wrote: 6) Ds question.
there were 2 questions. 50 said yes to both questions and 100 said No to both questions then whats the total number of people?
a) 20 said yes to question 1 and 20 said NO to question 1
b)20 said yes to question 2 and 20 said NO to question 2

If 50 said yes to both questions, I don't see how either statement can be true - Statement 1 tells us that only 20 said yes to the first question, when we know already that 50 people said yes to both the first question and the second question. There's something wrong with the wording of the question here.

In general, I'm curious where these questions are from, since some of them don't seem particularly representative of the real GMAT.

bsingh3 wrote: ...... please explain how to solve it ASAP..i have exAM in 1 day....thanks a lot

Good luck on your test!