Challenging GMAT ques-Explanations a must!!

[raviagni]

1)Larry saves x dollars per month. Will Larry¡¯s total savings one year from now exceed his present savings by at least $500 ? (Assume that there is no interest.)

(1) In 6 months Larry's total savings will be $900.
(2) In 3 months Larry's total savings will exceed his present savings by $150.
Statement 1 ALONE is sufficient to answer the question, but statement 2 alone is NOT sufficient.
Statement 2 ALONE is sufficient to answer the question, but statement 1 alone is NOT sufficient.
BOTH statements 1 and 2 TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient.
Each statement ALONE is sufficient to answer the question.
Statements 1 and 2 TOGETHER are NOT sufficient to answer the question.

2)If X is a decimal number, is the tenth digit of X a zero?

(1) 16X is an integer
(2) 8X is an integer
Statement 1 ALONE is sufficient to answer the question, but statement 2 alone is NOT sufficient.
Statement 2 ALONE is sufficient to answer the question, but statement 1 alone is NOT sufficient.
BOTH statements 1 and 2 TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient.
Each statement ALONE is sufficient to answer the question.
Statements 1 and 2 TOGETHER are NOT sufficient to answer the question.

3)What was the average (arithmetic mean) monthly rainfall during 1984 in region Y?

(1) In region Y the total rainfall for the first 6 months of 1984 was twice the total rainfall for the last 6 months of 1984.
(2) In region Y the average monthly rainfall for the first 6 months of 1984 was 2.31 inches more than the average monthly rainfall for the last 6 months of 1984.
Statement 1 ALONE is sufficient to answer the question, but statement 2 alone is NOT sufficient.
Statement 2 ALONE is sufficient to answer the question, but statement 1 alone is NOT sufficient.
BOTH statements 1 and 2 TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient.
Each statement ALONE is sufficient to answer the question.
Statements 1 and 2 TOGETHER are NOT sufficient to answer the question.

4)What is the range of (1/101 + 1/102 + 1/103 + ¡­¡­+1/150)?
0 to 1/2
1/2 to 1/3
1/3 to 2/3
2/3 to 1
1 to 4/3

5)The average of temperatures at noon time from Monday to Friday is 50, the lowest one is 45, what is the possible maximal range of the temperatures?
20
25
40
45
75

6)How many different prime factors does N have?

(1) 2N has 4 different prime factors.
(2) N ^2 has 4 different prime factors.
Statement 1 ALONE is sufficient to answer the question, but statement 2 alone is NOT sufficient.
Statement 2 ALONE is sufficient to answer the question, but statement 1 alone is NOT sufficient.
BOTH statements 1 and 2 TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient.
Each statement ALONE is sufficient to answer the question.
Statements 1 and 2 TOGETHER are NOT sufficient to answer the question.

Guys,explanations a must to discuss this post

[sujaysolanki]

Could you please post the questions individually ..thanks

[gabriel]

Hi raviagni,

Welcome to BTG. Your have broken a number of rules of the forum with this post. Please post one question per thread, you will get a much better response that way. You can see for yourself that your post is too cluttered and confusing, that can be avoided by posting one question per thread. Also make sure you post Problem solving questions in the PS section.

Regards.

[TSonam]

Here are my answers:

1) B
2) D
3) C
4) C - is there a typo in the way u wrote the question.?
5) B
6) B

what are the OA? I could provide explainations if i did get it right. too many questions to post explainations.

let me know.

[NSNguyen]

HI TSonam,
for question 2, could you explain me why the answer is D? This question seems quite difficut.

[raviagni]

Thanks BTG world to caution me...Much appreciated

[Yuke]

HI TSonam,
for question 2, could you explain me why the answer is D? This question seems quite difficut.

I think its B.

2)If X is a decimal number, is the tenth digit of X a zero?

(1) 16X is an integer

only a few decimal values satisfy this statement for X. They are the decimal equivalents of 1/16, 2/16, 3/16... or .0625, .125, .1875 etc. As you can see in all these possibilities, some contain zero in the tenths digit, and some don't. Thus this statement is insufficient to answer the question.


(2) 8X is an integer

using a similar analysis, the possibilities are .125, .250 etc. All these decimals don't have a zero in the tenths digit, so this information is sufficient to answer the question which is no.

[sankruth]

Q4: Is it supposed to be...

What is the range of (1/101 + 1/102 + 1/103 +... +1/150)?
0 to 1/2
1/2 to 1/3
1/3 to 2/3
2/3 to 1
1 to 4/3

1/101 is close to 1/100, hence almost 0.01.
1/150 = 0.0066

The max value can be 0.01 x 50 = 0.5 OR 1/2

The min value can be 0.0066 x 50 = 0.33 OR 1/3

The value must lie between 1/3 and 1/2 Choice B

[Auzbee]

6)How many different prime factors does N have?

(1) 2N has 4 different prime factors.
(2) N ^2 has 4 different prime factors.

1. 2N has 4 prime factors (PF). Then N should have 3 PF since 2 is a prime number. Sufficient.
2. N^2 has 4 different PF. Then N should have 4 PF. Sufficient.

Answer should be (D).

Anyone else would like to take a stab at this one?

[v_shiv]

It asks for "Different Prime Factors". If 2 is again a factor of N, then the number of the "Different Prime factors" will not be 3.

[camitava]

TSonam, I am not getting how u get D for this Qs and Yuke, how come B for this Qs -

2)If X is a decimal number, is the tenth digit of X a zero?
(1) 16X is an integer
(2) 8X is an integer

X is a decimal number, so it can be anything from .000000...1 to .999...999 or even 12121212....32323.000000...1
We somehow don't know the exact value of X.
Now By 1, suppose 16 * .0001 = .0016 and 16 * .9999 = 15.9984
By 2, suppose 8 * .0001 = .0008 while 8 * .0434 = 3.472 and 8 * .9999 = 7.9992
In both cases, we can not come to conclusion- IMO E.

[sujaysolanki]

Say x = 1/8 or 1/4 or 1/2 ...

From 1 16X is an integer ..not putting above values in 1 we get that tenth digit is not zero

Hence sufficient


From 2 also we get the same thing ..

Hope this helps