GMAT MATH : Word Problem - Geometry

Question

A point on the rim of a circular tire that is rotating in a plane is 6 inches from the center of the rim. What is the distance traveled, in inches, by this point in 10 seconds when the tire turns at the rate of 250 revolutions per minute?

A) 36000π
B) 6000π
C) 3000π
D) 500π
E) 1000π 

 Solution

 Answer D

Area covered by a circle is equal to its circumference, which is calculated by 2πR 
If a point is 6 inches from the center of the rim and it rotates in a circle, then radius (R) of the circle is 6 inches.
So the distance covered by one rotation of the rim is  2 (π) (6) = 12π
Distance cover in one minute; based on the information provided in the Question the rim makes 250 revolutions per minute.
Distance covered in 250 revolutions = 12 (π) (250).
The Question wants us to know how far the rim travels in 10 seconds. This can be calculated by multiplying the total distance traveled by (10/60) (10 seconds of 60 seconds of minute).
   12 (π) (250) (10/60) = 500π

 

 

Use of a Infinitive and a Participle

Use of a Infinitive and a Participle 

 Choosing between an infinitive and a participle, this is another type of question on the GMAT sentence correction questions.  In this type of question after eliminating all the obvious errors you will be struggling between two options; one will have an infinitive and the other will have a participle.

Like you may have to directly choose between 'to run' and 'running'. Both may sound equally correct to your ears, but only one of the two options is correct. Do not worry, in such a situation  we need to memorize a simple rule.

The Rule

An infinitive is almost always used to show intention or desire, whereas a participle is almost always used to show the result or effect of something. So use a present participle to show effect and infinitive to show intention.

Example,

Sentence 1: Sheldon drove his truck at 170 miles an hour, causing an accident.

Sentence 2: Sheldon drove his truck at 170 miles an hour to cause an accident.

In the sentence 1 the present participle 'causing' express the result or effect of driving at 170 miles per hour, whereas in the second sentence 'to cause' clearly suggests that Sheldon drove his truck at a particular speed with the intention of causing an accident.

Important Note: Here when you read the sentence, you need to understand the meaning of the sentence. Once you understand the meaning of the sentence it is very easy to decide between an infinitive and a participle.

AWA section on the GMAT

AWA Section on the GMAT

Anyone with an average hold on English can actually score a 6 on GMAT's Argument essay without putting too much time into it. One just needs to know how. The Awa Argument essay section is one of the compulsory sections on the GMAT. In this section the GMAT test takers try to test your writing skills and how good are you in analyzing flaws in a argument. It would be fair for me you say how well you identify flaws in someone's argument and how good are you in communicating the same in writing.

The given paragraphs on the AWA Argument essay will always exhibit some flaws in reasoning; while the types of flaws are potentially limitless, but most of them are not that complicated and one can easily survive the horror of AWA argument essay section.

What is expected from you?

You are expected to write a well structured analysis on the argument presented. You need to identify the flaws in the argument. Anything between 350 - 500 words will be sufficient for this task. People suggest writing about 500 words per essay - the reason being unless you're a good writer, it's difficult to convey what you want to say minimally. Since you only have 30 minutes in your hand for this task the GMAT asks for a "draft" version, not a very awesome finalized essay.

Points to Remember

1) You need to remember that Argument essay is more science than art. You need to use connecting words to "build up" your argument. ("Moreover", "for example", "to illustrate", ...; do not use "etc..." unless absolutely necessary, it looks like an open ending - make your argument sound robust and confident).. So, a bit of structure, good grammar and 3 argument loopholes (2 or 4 is fine, but 3 is a good number to stick to) are all the things that you need to write your essay.

2) It's also useful to keep in mind that one of your GMAT AWA test rater is an algorithmic e-rater. On top of that, from what I've read, the human graders seem to be so overburdened with essays to check that they too follow an "algorithm" almost the same as the e-rater; a longer essay is sure to score better than a shorter one.

3) Don’t worry about making too much sense in the essay. The e-rater can’t validate your facts and figures – it can only read structure. And the reader cannot verify any of them either – trust me, he doesn’t have the time or the inclination nor is he supposed to do so.

Sentence Correction Practice Question

Sentence Correction Practice Question

 Question

Rising raw material costs is only one of the factors, albeit an important one, that keeps the housing market from spiraling out of control, like it did earlier in the decade.

A) keeps the housing market from spiraling out of control, like it did

B) keep the housing market from spiraling out of control, as it did

C) keeps the housing market from spiraling out of control, as it did

D) keep the housing market from spiraling out of control, like

E) keep the housing market from spiraling out of control, like it did

Solution

Answer B

Remember the following rule

On the GMAT for sentences like this where the subject is "one of the factors ... that keeps.." you can follow this simple rule.

If you see the sentence in the form of

One of the Noun (Here Noun is always PLURAL) .... that/who ..... PLURAL VERB.

If you see the sentence in the form of (where that/who is not used in the sentence).

One of the Noun (Here Noun is always PLURAL) .......SINGULAR VERB.



The original sentence states that "a higher interest rate is only one of the
factors...that keeps..." The clause "that keeps the housing market from
spiraling out of control" is describing the word "factors." Since "factors" is plural
noun and "keeps" agrees with singular nouns, we need to find a sentence that
replaces "keeps" with "keep". Also, "like it did earlier in the decade" is
incorrect. When comparing clauses (i.e., a phrase containing a subject and
a verb), we must use "as" instead of "like." For example, "She sings like her
mother" and "She sings as her mother does" are both correct, but "She sings
like her mother does" is not.

GMAT Math : Data Sufficiency

GMAT Math : Data Sufficiency 

 Question

 How must is 60 percent of a certain number

Statement 1 : 25 percent of twice the number is equal to half the number.
Statement 2 : 50 percent of the number is 20 less than the number.

A) If statement 1 alone is sufficient to answer the question, but statement 2 alone is not sufficient.
(B) If statement 2 alone is sufficient to answer the question, but statement 1 alone is not sufficient.
(C) If both statements together are needed to answer the question, but neither statement alone is sufficient.
(D) If either statement by itself is sufficient to answer the question.
(E) If not enough facts are given to answer the question.

Solution:

 Answer B

Evaluating Statement 1: 25 percent of twice the number is equal to half the number.

 To determine what is 60 of a certain number (say x), you need to know what the value of that number (x) is. Statement 1 seems to provide that equation to solve for the value of x, but when you read this statement closely it is bogus leads you nowhere.

it states as
2 (0.25x ) = 0.5x
0.5x = 0.5x

You cannot solve for the value of x.

 Evaluating Statement 2: 50 percent of the number is 20 less than the number. 

 The Equation for this statement will be

0.5x = x-20
This implies,
x-0.5x= 20
Solving for 
0.5x =20
x=40

Since we know the value of X we can now find 60 percent of x.
So the correct choice is answer B

GMAT Math Practice - Coordinate Geometry

GMAT Math Practice - Coordinate Geometry 

Question

Line P is described by the equation 3x + 2y - 4 = 0.  Which of the following lines is parallel to P and has the same x-intercept as the line  5x - y + 5 = 0?
a) 6x = -5y + 20
b) -y = (3/2)x +20
c)  -4x - 6y =8
d)  y = -3x - 3
e) - 4y = -6x-12

Solution

 For some reason, many GMAT test takers seem to be confused with such a question and they immediately start by plotting points on the axes.

 You need to know simple rule for parallel lines.

Lines are parallel when they have the same slopes, and the slope is easiest to see when a line is written in slope intercept from y = mx + b.

Converting P to that form we get
y = -3x + 4 or
y = -3x + 4
So the slope of any parallel line will be -3. The second condition is given by the 2nd equation.  Its x-intercept is the x-value where y = 0.

That is 5x - 0 + 5 = 0
5x = -1 so
x = -1 .

For each of the given answer choices, we can start by looking for either a matching slope or x-intercept, and then if it matches one, see if it matches both.

Answer D is y = -3 x - 3.

y = -(3)x -3

Therefore the slope is -3, and parallel to P.  Furthermore, substituting in x = -1.y = -3 x -3

y = 3 - 3 = 0 

So this line also has the desired x intercept.