How to ace the GMAT in 28 days: Day 12 (analysing day 11)

Another 690. Lesson learned today: a bottle of red the night before, followed by doing the test at 5am since I’ve got no other slot available, does not contribute to a higher GMAT score. 108 questions, 52 quant and 56 verbal, and 11 wrong maths and 5 English errors giving with corrected raws of 38Q/50V.

Quant

A Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C BOTH statements (1) and (2) TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D EACH statement ALONE is sufficient.
E Statements (1) and (2) TOGETHER are NOT sufficient.

If √d is a positive integer, is d greater than 15?

(1) d is divisible by 25.
(2) d is divisible by 40.

I chose B, but it’s a silly mistake. Statement 1 means d could be anything: 25, 50, 75, 100… and Statement 2 says basically the same thing, but that d could be 40, 80, 120, 160 and so on, some of which root to less than 15. Rattled I got this wrong, especially when a 700 GMAT was only a point away.

What is the value of 2x^2 + 4y?

(1) x = 3
(2) x^2 + 2y = 17

I got it wrong with D, despite discounting Statement 1, knowing x alone doesn’t say much about y. But statement 2 actually restates 2x^2 + 4y (just halved in value) and gives the solution: 17, meaning the equation in the question must equal 34. B is the answer. Silly mistake again.

Is | x + 2 | < 3?

(1) x < 1
(2) x > -5

Another silly error. I chose A. Thinking that x must be less than 1 ( x -5, there are three possible positions, -4, -3, -2, which is a range of 3.) Grrr, another daft mistake. The answer is C.

If n is a positive integer, what is the tens digit of n?

(1) The hundreds digit of 10n is 6.
(2) The tens digit of n + 1 is 7.

I chose E. How many more daft mistakes am I going to make today? This is a real danger: on the computer-adaptive GMAT, where the difficulty (and therefore scoring potential) of a question depends on what you got right before it, it’s vital to get the easy ones right or the sequence of 37 questions thrown up will contain too many easy ones, lowering your potential for acing it dramatically.

Statement 1 tells us the number 10n is something like 6xx. So n must be between 60 and 69 and the tens digit must be 6. Statement 1 is enough alone. Knowing the tens digit of n+1 is 7 doesn’t help much except in conjunction with statement 1(it means n must be 69, since adding one pushes n into the seventies.) Statement 1 alone can tell us the tens digit of n must be 6. The answer is A.

If y = 3x + 2 and y = – 4 – 6x what is the value of y?

(A) -2/3
(B) 0
(C) 2
(D) 8
(E) 16

Finally a maths question I’m not kicking myself for getting wrong. I chose D and wasn’t sure about it. This pair of simultaneous equations (I need to brush up on sim eqs, but for now let’s substitute) has a trap or two. Would solving the sim eq be faster than substituting, in the heat of the exam?

-2/3 = 3x + 2 so 3x = -2 2/3 and -2/3 = -4 – 6x

If y is -2/3, then 3x = -2 2/3 and -6x = 3 1/3, so A’s out. If y is 0, then 3x = -2 and 6x = -4, so B’s in with a chance. Let’s try C: 3x = 2 and 6x = -4, again a negative making it wrong. D results in 3x = 6 and 6x = -12, negative again. E results in 3x = 14 and 6x = -20, clearly wrong. The answer is B.

How many different groups of 3 people can be formed from a group of 5 people?

(A) 5
(B) 6
(C) 8
(D) 9
(E) 10

I guessed C; too close to the time limit to worry about permutations and combinations. Number of combos of n things taken r at a time is n!/r!(n-r)! That’s 5*4*3*2*1 / 3*2*1(2*1), which is 120 / 6(2), which is 120/12. The answer is E.

In a certain sequence, the term xn is given by the formula xn =2xn-1 – 1/2(xn-2) for all n ≥ 2. If x0=3 and x1=2, what is the value of x3?

(A) 2.5
(B) 3.125
(C) 4
(D) 5
(E) 6.75

I guessed A. Sequences are unfamiliar animals in the GMAT. Let’s see… substituting x3, we get 2 x2 minus a half of x1… so we need to find x2… which, substituting x2, gives 2*1 minus a half of x0 … which is 4 minus 1.5 … 2.5.

Substituting this value of x2 back into the first equation to find out x3, we get 2 x 2.5 – 1.2(2), which is 4. The answer is C, which I didn’t need to look up, but took me more than four minutes to solve.

Fox jeans regularly sell for $15 a pair and Pony jeans regularly sell for $18 a pair. During a sale these regular unit prices are discounted at different rates so that a total of $9 is saved by purchasing 5 pairs of jeans: 3 pairs of Fox jeans and 2 pairs of Pony jeans. If the sum of the two discounts rates is 22 percent, what is the discount rate on Pony jeans?

(A) 9%
(B) 10%
(C) 11%
(D) 12%
(E) 15%

Ran out of time at the end of this section. I chose E. But it’s simple arithmetic: let Fox jeans be f and Pony jeans be p, which means three pairs of Foxes and two pairs of Ponys are 3*15 and 2*18. 3f + 2p = $81 at normal prices. $9 was saved from this $45 and $36, each by discounting less than 22%.

Use my head first: Ponys are a smaller proportion of the total price, so needed a higher discount that Foxs. That suggests A, B, and maybe C won’t work. Let’s see what E would have got: Ponys at 15% off would mean Foxs at 7% off. 7% of $45 + 15% of $36: $3something and $5something, not enough. On to D: 10% off Foxs and 12% off Ponys: $4.50 + $4.32 = still not exact. Can’t be C since they’d never make it a straight 11:11 split, so try B: 12% off Foxes and 10% off Ponys = $5.40 $3.60 = $9. The answer is B after all.

For all integers a, b, c, and d, *(a, b, c, d) is defined as a – b + c – d. What is the value of *(1, 3, 8, 5)?

(A) – 1
(B) 0
(C) 1
(D) 2
(E) 3

I chose D. Of course it’s C: (1-3 + 8-5) = 1. Simple. Another silly mistake.

If x – 3y = – 20, then 2x – 6y =

(A) – 40
(B) – 10
(C) 0
(D) 10
(E) 40

I chose E. The second simple equation just doubles the first, so the answer will double too. It’s A.

If 5 – 6/x = x then x has how many possible values?

(A) None
(B) One
(C) Two
(D) A finite number greater than two
(E) An infinite number

I put E, thinking that x could be anything fractional or decimal and not thinking to move the divisor x across to the other side of the equation. If you rearrange to 5-6 = x^2 then x can only be -1 or 1. It’s C.

That’s a total of EIGHT problems I really should have got right in the quantitative section. Lesson learned: this practice test could so easily have been a 720, just with a slightly higher level of care and a slightly lower level of residual blood/alcohol.

Verbal

New observations about the age of some globular clusters in our Milky Way galaxy have cast doubt on a long-held theory about how the galaxy was formed. The Milky Way contains about 125 globular clusters (compact groups of anywhere from several tens of thousands to perhaps a million stars) distributed in a roughly spherical halo around the galactic nucleus. The stars in these clusters are believed to have been born during the formation of the galaxy, and so may be considered relics of the original galactic nebula, holding vital clues to the way the formation took place.
The conventional theory of the formation of the galaxy contends that roughly 12 to 13 billion years ago the Milky Way formed over a relatively short time (about 200 million years) when a spherical cloud of gas collapsed under the pressure of its own gravity into a disc surrounded by a halo. Such a rapid formation of the galaxy would mean that all stars in the halo should be very nearly the same age.
However, the astronomer Michael Bolte has found considerable variation in the ages of globular clusters. One of the clusters studied by Bolte is 2 billion years older than most other clusters in the galaxy, while another is 2 billion years younger. A colleague of Bolte contends that the cluster called Palomar 12 is 5 billion years younger than most other globular clusters.
To explain the age differences among the globular clusters, astronomers are taking a second look at “renegade” theories. One such newly fashionable theory, first put forward by Richard Larson in the early 1970’s, argues that the halo of the Milky Way formed over a period of a billion or more years as hundreds of small gas clouds drifted about, collided, lost orbital energy, and finally collapsed into a centrally condensed elliptical system. Larson’s conception of a “lumpy and turbulent” protogalaxy is complemented by computer modeling done in the 1970’s by mathematician Alan Toomre, which suggests that closely interacting spiral galaxies could lose enough orbital energy to merge into a single galaxy.

The passage suggests that Toomre’s work complements Larson’s theory because it

(A) specifies more precisely the time frame proposed by Larson
(B) subtly alters Larson’s theory to make it more plausible
(C) supplements Larson’s hypothesis with direct astronomical observations
(D) provides theoretical support for the ideas suggested by Larson
(E) expands Larson’s theory to make it more widely applicable

I chose E. But Toomre’s 1970’s mathematical modelling doesn’t expand Larson’s theories; Larson may not even have been around at the time, so the timeline doesn’t work. The clue’s in that only one answer relates Larson to Toomre without suggesting the two men had anything to do with each other; it’s not causation, it’s coincidental correlation. It’s D.

During the 1960’s and 1970’s, the primary economic development strategy of local governments in the United States was to attract manufacturing industries. Unfortunately, this strategy was usually implemented at another community’s expense: many manufacturing facilities were lured away from their moorings elsewhere through tax incentives and slick promotional efforts. Through the transfer of jobs and related revenues that resulted from this practice, one town’s triumph could become another town’s tragedy.
In the 1980’s the strategy shifted from this zero-sum game to one called “high-technology development,” in which local governments competed to attract newly formed high-technology manufacturing firms. Although this approach was preferable to victimizing other geographical areas by taking their jobs, it also had its shortcomings: high-tech manufacturing firms employ only a specially trained fraction of the manufacturing workforce, and there simply are not enough high-tech firms to satisfy all geographic areas.
Recently, local governments have increasingly come to recognize the advantages of yet a third strategy: the promotion of homegrown small businesses. Small indigenous businesses are created by a nearly ubiquitous resource, local entrepreneurs. With roots in their communities, these individuals are less likely to be enticed away by incentives offered by another community. Indigenous industry and talent are kept at home, creating an environment that both provides jobs and fosters further entrepreneurship.

The passage suggests which of the following about the majority of United States manufacturing industries before the high-technology development era of the 1980’s?

(A) They lost many of their most innovative personnel to small entrepreneurial enterprises.
(B) They experienced a major decline in profits during the 1960’s and 1970’s.
(C) They could provide real economic benefits to the areas in which they were located.
(D) They employed workers who had no specialized skills.
(E) They actively interfered with local entrepreneurial ventures.

D was my reluctant choice. With fresh eyes, I see it’s C: that’s the whole point of the passage. A and B and E aren’t backed up, D is only hinted at. It’s C.

In many upper-class Egyptian homes, French was spoken within the family, just as it had once been among the Russian aristocracy.

(A) just as it had once been among the Russian aristocracy
(B) just like it once had been among the Russian aristocracy
(C) just as the Russian aristocracy had once done
(D) similar to what the Russian aristocracy had done once
(E) like what had once been done by the Russian aristocracy

One of those sentence correction questions I hate: a thicket of tortuous verbiage to hack through for sense. I chose B, looking for the agreement of ‘once had been’. But the ‘like’ in B looks clumsy. It’s A.

The failing of the book lies not in a lack of attention to scientific detail but in the depiction of scenes of life and death in the marine world with emotional overtones that reduce the credibility of the work.

(A) depiction of scenes of life and death in the marine world with emotional overtones that
(B) fact that it depicts marine world scenes of life and death as having emotional overtones that
(C) depiction of scenes of life and death in the marine world, whose emotional overtones
(D) depiction of marine world scenes of life and death, which have emotional overtones and thus
(E) fact that it depicts scenes of life and death in the marine world, whose emotional overtones amount of new jobs to be created during the reporting period and the amount of hours to be worked.

My choice: D. More wordy brambles. All the answers are either overly verbose or use pronouns incorrectly: whenever a pronoun could refer to more than one antecedent it’s wrong (as in C and E). Once again it’s unchanged with A.

Four generations of Americans have developed the habit of reading the daily newspapers due to the comic strips being appealing.

(A) due to the comic strips being appealing
(B) because of the appeal of the comic strips
(C) for the fact of the comic strips’ appeal
(D) as a result of the comic strips having appeal
(E) since the comic strips were appealing

I chose A. But that doesn’t link comic strip strongly enough to newspapers. C and D sound okay, but both add in extra words (fact, result) that aren’t needed or used in the original. And E changes the sense of the sentence to make the comic strips sound incidental rather than central. It’s B.

So: lots of silly mistakes this test, when I should have scored into the 700s. Must. Concentrate. More.

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