solidcolor's mezzanine

SC1000 - 301-320: 17/20 (85%)

Incorrect: 304, 307, 309.

32)

The numbers we have are: -2, 1, 5, 8 and n. If n is less than or equal to 1, the median is always 1. But, for n>2, the median is n (for example for n=2, median is 2, for n=3, median=3) but for n>=5, median is always 5.

According to (1), median is less than 5. In order for this to happen, n must be greater than 2 and less than 5. That lies within (0,7) and therefore, this statement is sufficient.

According to (2), median>1. For this to happen, n should be greater than 2 as we said before. But, if n=10, then the median is 5 again. Therefore, we do not know if n lies in (0,7) and therefore, this statement is insufficient.

22)

Large ticks: 1/5, 2/5, 3/5, 4/5, 5/5, or 7/35, 14/35, 21/35, 28/35, 35/35

Small ticks: 1/7, 2/7, 3/7, 4/7, 5/7, 6/7, 7/7 or:
5/35, 10/35, 15/35, 20/35, 25/35, 30/35, 35/35.

The smallest distance is (21/35)-(20/35) = 1/35.

14)

From the 4 given expressions, only two of them give a product in the x^2 - b^2y^2 fashion: x+y and x-y with product x^2 - y^2 (b=1). All the other expressions, if multiplied, will result in the appearence of the xy factor.

Therefore, the probability is 2/4 = 1/2

The total number of marbles is b+r+w. The probability that red marbles are chosen is P1 = (b+r+w r) Excuse me for the notation but I do not know how else to write it..

The probability that white marbles are chosen is P2 = (b+r+w w). We must compare P1 to P2:

P1 = (b+r+w)! / r!(b+w)! (1)

P2 = (b+r+w)! / w!(b+r)! (2)

P1 / P2 = w!(b+r)! / r!(b+w)! (3)

Since w r and b are positive integers, w! < (w+b)! (4)

Therefore, (3) becomes:

P1 / P2 = w!(b+r)! / r!(b+w)! < (w+b)!(b+r)! / r!(b+w)!, or

P1 / P2 < (b+r)! / r! and hence P1 < P2.

It seems to me that the statement itself is sufficient.

If n is not a factor of 2, then it can be for example 3 or 7 or 11:

For n=2, r=3
For n=7, r=0
For n=9, (9^2-1^2) / 24 gives r = 1 (80/24 = 10/3).
Therefore, we cannot determine r with the first assumption.

If n is not a factor of 3, let it be 2 or 4 or 8:

For n = 2, r=3
For n = 4, r=15
For n=8, r=5 (63/24=21/8)

We cannot determine r here either.

Therefore, no statement is sufficient.

I'm back. It's time for CR.

29 Sept: CR1000, Test III: 12/20 (not taking time into account)
30 Sept: CR1000, Test II: 16/20 (not taking time into account)

I'll try to bring it up...

SC1000 (did long time ago):

Q310- Q384: 15 incorrect, hit rate 80%.
Q385- Q410: 9 incorrect, hit rate 58%.

Man it fluctuates like hell. I'll give a better try today.

Are you going over your errors and learning lessons from them? Your hit rates fluctuate so much that it seems like it really just depends on the difficulty of the question.

You make a good point. It depends more on my health conditions, physical and mental, on the weak knowledge ground...

I learned some from the errors anyway. But I forgot quite a lot...

Yeah, IMO if your hit rate is fluctuating that drastically given those factors, it's a good sign that you're fundamentals are quite as strong as they should be. Have you gone through MGMAT's SC book?

Yes I did, I revise it quite many times. The hardest thing to remember is IDIOMS. The hardest rules are COMPARISONS.

I need to be more stable.

Thanks for your encouraging words.

Just stick with it and you'll do fine. Think about creating an error list of SC's that you've missed and compare them for common mistakes and look for common "clues" that will help you see the error next time around.

It's really hard to study at night after a full day working hard... I feel better to study at weekend.

mayonnai5e, this is my hit rate for CR (I feel I am weak in CR, as my logic mind is so poor):

CR1000:

Test 2: 16/20
Test 3: 17/20
Test 4: 18/20
Test 5: 17/20
Test 6: 17/20
Test 7: 18/20
Test 8: 20/20

A number of of questions are repeated from OG. Some of them I felt the same difficulty and got incorrect answers again...

Anyway I am glad that I'm getting better in CR, feeling more confident in reasoning for the right answers.

I think the most important thing is your confidence in countering the questions. When you feel you are confident, and in deed feel comfortable in drawing answers, you master it.

More practice and more practice. This is the second time I study for GMAT but I never get fed up.

Fun for a while, how many times did I repeat the word or refer to "the feeling" in the previous post? No wonder why I am poor in logic. (Assumption: Feelings are illogical).

Studying GMAT is fun but not easy. All types of disturbance may occur and seriously affect the study.

Anyway anyway...

SC1000, Q411-Q536 (125 questions): 25 incorrect.

Hit rate: 80%.

I've gotta bring this up. 90%, is it possible? Last week I wasn't concentrated.

I'm gonna make a collection of wrong-answered questions out of this SC1000 set, and try them again. I've gone half the set.

Still in love with GMAT. It's fun.

Q700-799: 16 incorrect. Hit rate 84%.

Q600-699: 25 incorrect. Hit rate 75%.

Q500-599: 22 incorrect. Hit rate 78%.

Q400-499: 15 incorrect. Hit rate 85%.

Q300-399: 25 incorrect. Hit rate 75%.

Q200-299: 25 incorrect. Hit rate 75%.

Q100-199: 23 incorrect. Hit rate 77%.

Q1-99: 20 incorrect. Hit rate: 80%.



What can we tell from this?

There are some repeated mistakes. There are many new concepts (idioms, word usages, etc.) There are careless errors.

I'm gonna stop right here and start revising the 800 questions again. I'm getting scared now...