Search found 1085 matches


This one got my attention Firstly, the linear function can either increase or decrease, BUT it cannot increase and decrease at the same time. If the latter is a case, then we don't have a linear function. The question explicitly states that f is a linear function, i.e. f(x)=ax+b where a is the slope...

by pemdas

Wed Feb 27, 2013 4:38 pm
Forum: Data Sufficiency
Topic: Function
Replies: 8
Views: 1714

This problem can be easily solved if we use the vector product rule. We first, find the difference between one point and two other points, and then find the vector product. The whole work is also derived algebraically to avoid matrix manipulations such as S=|(X�-X₃)•(Y₂-Y₃)-(X₂-X₃)•(...

by pemdas

Tue Feb 26, 2013 4:46 pm
Forum: Problem Solving
Topic: coordinate geometry
Replies: 5
Views: 1389

To answer the mathematical doubts of three users above with regard to the quoted question, I would use Cramer's rule for solving the system of three linear equations with three unknowns. We have to define whether a determinant (det) of the matrix (underneath shown) is equal to 0 or it's not. |1 2 3|...

by pemdas

Tue Feb 26, 2013 11:06 am
Forum: Problem Solving
Topic: Equations - Number of solutions
Replies: 5
Views: 1246

first of all, this q. is well beyond GMAT :) secondly, the main trick here is that all q. choices contain only one variable (it doesn't matter what it states a or b or a+b, we speak about the number of variables), but the target function, For which function f below will g(a + b, a + b) = g(a, a) + g...

by pemdas

Thu Feb 21, 2013 3:50 pm
Forum: Problem Solving
Topic: How to solve these FUNCTIONS?
Replies: 3
Views: 875

answering to the original q. in this thread d/dx=4x-4=0, x=1 and d/dy=6y-12=0, y=2 d^2/dx^2=4 (implies min x) and d^2/dy^2=6 (implies min y) min f(x,y) = 2*(1^2) +3*(2^2)-4*1-12*2+18=4 and choice C Using multivariate calculus turns the solution of this q. into joke :) Find the minimum value of an ex...

by pemdas

Wed Feb 20, 2013 6:41 pm
Forum: Problem Solving
Topic: Minimum value of an expression
Replies: 65
Views: 36431

For all non-negative integers x and n such that 0 ≤ x ≤ n, the function f(x,n) is defined by the equation f(x,n) = x^(n–x) . The smallest value of n for which the maximum of f(x,n) occurs when x = 4 is (A) 6 (B) 7 (C) 8 (D) 9 (E) 10 f(x,n)=x^(n–x) d/dx = -x^(n-x-1)*(-n+x+x ln(x)), for x=4 w...

by pemdas

Tue Feb 19, 2013 8:37 am
Forum: Problem Solving
Topic: Help Functions!
Replies: 6
Views: 1074

winnerhere wrote:Y = 25x - x^2

Find the value of X , for which Y attains maximum value.

How to proceed with this question

Thanks in Advance,
Sai
Calculus :)
d/dx=25-2x, optimum is x=12.5
d^2/dx^2=-2 and we attain max Y at 12.5

by pemdas

Tue Feb 19, 2013 7:09 am
Forum: Problem Solving
Topic: Maximum value of a function
Replies: 16
Views: 2233

What is the maximum possible number of chocolate bars per hour produced by a machine? (1) Currently, the machine produces 1,200 chocolate bars per hour. (2) If the chocolate bar production rate is increased from half the machine's maximum rate by 300 chocolate bars per hour, the rate is increased b...

by pemdas

Mon Feb 18, 2013 6:41 pm
Forum: Data Sufficiency
Topic: maximum possible number of chocolate bars per hour- DS quest
Replies: 2
Views: 1520

IF a(b)=(2a-b)/(2b-a) THEN b(a)=(2a- (2a-b)/(2b-a)) / (2*(2a-b)/(2b-a) - a) Simplifying, b(a)=b/(2b-a) / (2a-b)/(b-a) = b(b-a) / (2b-a)(2a-b) We compare a(b) and b(a) OR (2a-b)/(2b-a) and b(b-a) / (2b-a)(2a-b) We may cancel out (2b-a) in the denominators to get (2a-b) and b(b-a)/(2a-b) Further we ma...

by pemdas

Sun Feb 17, 2013 3:55 pm
Forum: Data Sufficiency
Topic: DS - interesting problem
Replies: 8
Views: 1371

yes your logic is sound. One angle, x, is greater than another angle y to tell us that PQ has less inclination and less length than the other line segment. To help your thinking, imagine PQ as geometrically posed line segment in right triangle being a hypotenuse or placed on the space and starting f...

by pemdas

Sat Feb 16, 2013 9:28 am
Forum: Data Sufficiency
Topic: Data Sufficient Geometry Question - advice to tackle
Replies: 6
Views: 961

one function becomes another function, this is meant by the expression. f(x)=not (1-x) but f(1-x). We are looking for the values of all x to satisfy two functions not defined precisely - only their arguments are given (as x and x-1). By supplying x and x-1 into the functions below we should get the ...

by pemdas

Sat Feb 16, 2013 9:21 am
Forum: Problem Solving
Topic: Seeking help with f(x) question. Thanks!
Replies: 4
Views: 889

nice, you have a constraint here that x<90. Then answer is A. You missed some info interpreting q.

Orla M wrote:It's one of the GMAC practice tests. Here is camera shot showing that Answer A is the correct answer - solution 1 being sufficient.


Image

by pemdas

Sat Feb 16, 2013 8:26 am
Forum: Data Sufficiency
Topic: Data Sufficient Geometry Question - advice to tackle
Replies: 6
Views: 961

Hi again, there will be another couple of postings and thanks in advance for sharing your approaches on these questions. The question in this instances asks: If P is a positive integer, what is P? 1) p/4 is a prime number 2) p is divisible by 3 st(1) p=(2^2)*a where a is prime number. Since p>0 and...

by pemdas

Sat Feb 16, 2013 7:52 am
Forum: Data Sufficiency
Topic: DS integer properties: all possibilities eliminated?
Replies: 2
Views: 696

Am seeking your help with the following, thanks! I am given two parallel lines as in the image I have attached. PS being parallel to QR. The question asks whether the line segment PQ is smaller in length than the line segment SR. Two angles are given and I see that y is also at angle PSR by deducti...

by pemdas

Sat Feb 16, 2013 7:28 am
Forum: Data Sufficiency
Topic: Data Sufficient Geometry Question - advice to tackle
Replies: 6
Views: 961

The profit function when Company C produces and sells x units of Product R is P (x) = k(x – a)(x – b), where k, a, and b are constants and k < 0. What is the maximum value for P(x)? (1)P(20) = P(1,020) = 0 (2)P(120) = 9,000 yes, I agree Ron. Intuitively, I have subtracted (1020-20)/2 instead of...

by pemdas

Sat Feb 16, 2013 6:13 am
Forum: Data Sufficiency
Topic: The profit function when Company C
Replies: 10
Views: 1750