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I'm a quant-only tutor. The 3 biggest mistakes in quant prep I see in my students are: 1. Studying too little time a day: minimum 2 hours a day is required for quant only 2. Not studying the theory: read the theory in Manhattan books and solve the warmup problems there 3. Not solving problems by you...

by tutorphd

Wed Aug 08, 2012 7:58 am
Forum: GMAT Strategy
Topic: Looking to set up a study plan to improve my Score.
Replies: 2
Views: 906

Piracetam is for long studying to get the work done without procrastinating. It doesn't give you a sufficient speed boost to be worth taking it during an exam. I buy it on Amazon in bulk.

During the exam you will need actual stimulant like caffein etc.

by tutorphd

Thu Aug 02, 2012 3:55 pm
Forum: GMAT Strategy
Topic: Any advice on how to cope with morning groggyness?
Replies: 5
Views: 1519

My mental focus and speed usually reaches peak around 7pm. If you can't function in the morning, do not schedule your exam at that time. The only thing to give you focus, when you are usually sleepy, is a stimulant. In order of increasing strength: ginseng, coffee, ephedra, ritalin etc. To offset fa...

by tutorphd

Thu Aug 02, 2012 9:31 am
Forum: GMAT Strategy
Topic: Any advice on how to cope with morning groggyness?
Replies: 5
Views: 1519

Because the permutation calculation of 960 favorable permutations in each scenario treats each card as distinguishable by number or suit or both - that is implicit in the calculation used to get 960. You don't correct there for 2 in suit A and 2 of suit B "being the same". That is why, when you conv...

by tutorphd

Tue Jul 31, 2012 7:47 pm
Forum: Problem Solving
Topic: Combinations Randolph Question - Need expert help
Replies: 8
Views: 1609

This question definitely takes long time because you have to trace many possibilities. I classify it as "equations in integers". x = new books; y = used books sales: 15x+10y=125, looking for non-negative integer solutions for x and y profit: 5x+2y Always simplify equations in integers to lowest poss...

by tutorphd

Mon Jul 30, 2012 7:16 pm
Forum: Problem Solving
Topic: Need expert help - Fastest method to solve this question
Replies: 5
Views: 1306

The theorem applies only when you are selecting from a set of different objects. If some of the objects are not different/distinguishable, not all combinations will correspond to the same number of permutations, and the number of permutations and combinations are not related so easily by a simple di...

by tutorphd

Sun Jul 29, 2012 5:02 pm
Forum: Problem Solving
Topic: Combinations Randolph Question - Need expert help
Replies: 8
Views: 1609

The test has no infinite difficulty questions so they do plateau. If you keep answering them correctly, the questions in a certain topic will plateau to high difficulty. If the next question is from a different topic, the test may start probing from middle level, to establish your proficiency in tha...

by tutorphd

Sun Jul 29, 2012 3:39 pm
Forum: GMAT Math
Topic: Question on difficulty scaling of math questions
Replies: 4
Views: 1378

The most efficient approach to this problem is neither combinations nor permutations but using the slot principle (multiply possibilities for each slot): total combinations = (ways to choose two pair cards) x (ways to choose two non-pair cards) ways to choose two pair cards = 6 because there are 6 p...

by tutorphd

Sun Jul 29, 2012 3:29 pm
Forum: Problem Solving
Topic: Combinations Randolph Question - Need expert help
Replies: 8
Views: 1609

Your calculation of 12*1*10*8 = 960 permutations only includes the scenario in which the first two cards form a pair, and the other two don't. There are additional scenarios. If P denotes a pair card and N denots a non-pair card, there are 6 different scenarios (anagrams of PPNN): PPNN NPPN NNPP PNN...

by tutorphd

Sun Jul 29, 2012 3:18 pm
Forum: Problem Solving
Topic: Combinations Randolph Question - Need expert help
Replies: 8
Views: 1609

The two statements together are not sufficient because of the weird behavior of numbers between 0 and 1: If 0 < x < 1, raising it to higher power brings the result closer to zero, so sqrt(x)>y and x>y do not guarantee that x^3 (which is brought closer to zero) will remain larger than y. If we knew t...

by tutorphd

Sun Jul 29, 2012 12:16 am
Forum: Data Sufficiency
Topic: is x^3>y>
Replies: 2
Views: 716

1. is sufficient because you can calculate the position of the meeting point from the time 2 hours and the average speed of one of the trains.

by tutorphd

Sun Jul 29, 2012 12:07 am
Forum: Data Sufficiency
Topic: Two trains
Replies: 1
Views: 612

1. interpreted means that y and z have the same signs, only then their abs values will add up. Not sufficient because we don't know the sign of x. 2. interpeted means that x and y have the same signs. Not sufficient because we don't know the sign and magnitude of z. 1+2. together mean that x and y a...

by tutorphd

Sat Jul 28, 2012 11:58 pm
Forum: Data Sufficiency
Topic: Is x(y+z)>=0?
Replies: 1
Views: 666

The way the problem is stated, I get E also. There must be a typo, either in the problem or in the answer.

by tutorphd

Sat Jul 28, 2012 11:53 pm
Forum: Data Sufficiency
Topic: The decimal representation of x
Replies: 4
Views: 1302

Statements (1) and (2) together, give two different possible scenarios: a) ABC is not one of the right angles -> ABC + BCD =180, ABC = 2BCD -> ABC = 120, BCD = 60 -> YES b) ABC is one of the right angles -> BCD = 45 -> Sum of the other two angles is 360-90-45=225, one of them is 90 and the other is ...

by tutorphd

Sat Jul 28, 2012 11:40 pm
Forum: Data Sufficiency
Topic: Equal to 60?
Replies: 3
Views: 891

This is a periodic sequence. The sum of one period is 2+(-3)+5+(-1)=3. There are 24 periods till a_96, inclusive. Add 24 periods and a_97 for the total sum.

by tutorphd

Sat Jul 28, 2012 11:26 pm
Forum: Problem Solving
Topic: What is the sum?
Replies: 2
Views: 903