Problem Solving

heymrdj wrote:what level would you say this question is? 600? 700? Mid-700+?

VP_Jim wrote:I'm going to side with Ron on this one - sure, you might be able to solve it using algebra. But, picking numbers is foolproof once you get the hang of it, and it's a universal strategy for any problem that says "in terms of" and some problems that don't.

The best GMAT strategies are those that turn complex equations into simple math, and that are applicable to many problems. Plugging in numbers is one of those strategies.

Good question, Ron.

ghacker wrote:This is a very easy question

I thinks its in the most lowest level ( say level 100---- if their is such a one )




"TThree Grades of milk are 1 percent, 2 percent and 3 percent fat by volume. If x gallons of the 1 percent grade, y gallons of the 2 grade, and z gallons of the 3 percent grade are mixed to give x + y + z gallons of a 1.5 percent grade, what is x in terms of y and z "

First thing is to read the question properly

Then u understand that the % is a buff it has no bearing on the result
so forget about the % and focus on the numbers

2.0 The numbers are 1 ,2, 3 and 1.5 ----> If you look at the numbers
you see that they are multiples of 0.5 that is

1 = 0.5*2 ; 2 = 0.5*4 ; 3 = 0.5*6 and 1.5 = 0.5*3

So know u can for get about the 1,2,3,and 1.5 , and concentrate on the
2,3,4and 6

So now you see that the answer is

X = Y+3Z

N.O wrote:Not sure whether the post above (picking a number) is necessarily the best and most efficient solution. Here is a general solution - no picking numbers where any mistakes could happen.

The general formula that we can write as soon as we read:

0.01x+0.02y+0.03z=0.015(x+y+z) /lets multiply everything by 1000 to make things easier

[Exp of the formula above:
0.01x+0.02y+0.03z===adding up all those milks with different fat
0.015(x+y+z)==total amount with mixed fat (1.5%)]

10x+20y+30z=15x+15y+15z --> 5x=5y+15z or x=y+3z --> Ans A.