Some doubts in PS and DS

[This topic has 1 expert reply and 2 member replies]
Forum Index GMAT Math
Free $100 Amazon.com Gift Card - Buy a GMAT course using a Beat The GMAT discount code between Mar 8-22 and get a $100 Amazon.com Gift Card. Learn more!
Post New Topic   Post Reply

Caps
Just gettin' started!

Default Avatar

Joined: 11 Feb 2007
Posts: 19

Thanks given: 0
Thanked 0 times in 0 posts
Topic: Some doubts in PS and DS
PostTue Feb 20, 2007 10:58 am
Elapsed Time:
00:00
 Lap   Why a timer is critical to improving your score
Can someone help me on this?? need explainations:

PS 1
How many integeres between 324700 and 458600 have a tens digit 1 and a units digit 3?

PS 2
In n is an integer which of the following CANNOT be a factor of 3n+4?
a)4 b)5 c)6 d)7 e)8

DS 1
If a and b are positive integeres what is the value of a+b?
1) a/b = 5/8
2) The greatest common divisor of a and b is 1


tnks for your help guys
Back to top
View user's profile Send private message
ktr32
Just gettin' started!

Default Avatar

Joined: 12 Feb 2007
Posts: 7

Thanks given: 0
Thanked 0 times in 0 posts
PostTue Feb 20, 2007 11:20 am
I will try to answer the questions 1 & 2, correct me if I am wrong.

Q1.
looking for how many times 13 appears between 324700 and 458600. 13 will only appear once every 100 number so: subtract 324700 from 458600 , then divide by 100, to how many times 13 will appear

458600 - 324700 = 133900 => 133900/100 = 1339, therefore the number 13 would appear 1339 times.


Q2. Best way is to plug in numbers for n, try {1,2,3,4,5} this should good picture.

3(1) + 4 = 7
3(2) + 4 = 10
3(3) + 4 = 13
3(4) + 4 = 16

From this you can eliminate a, b d, e thus only leaving c as your answer.
Back to top
View user's profile Send private message
banona
Rising GMAT Star

Default Avatar

Joined: 30 Dec 2006
Posts: 38

Thanks given: 0
Thanked 0 times in 0 posts
PostTue Feb 20, 2007 3:58 pm
here is my thoughts about the third question,
DS 1
If a and b are positive integeres what is the value of a+b?
1) a/b = 5/8
2) The greatest common divisor of a and b is 1

1- first statement ;isnot suffisant at all

2- second statement tells that the GCF of both a and b is 1, it is also insuffisant but we cab conclude that a and b are both products of different prime numbers ( I mean no factor of a is alsoa factor of be neither is it divior of it)

combining 1 and 2, we conclude that 5/8 is not a simplified fraction of a/b, therfore, a is 5 and b must be 8.

So a+b = 13

I hope I am right
_________________
I appologize for my Frenchy-English.
I am working on it.
Back to top
View user's profile Send private message
Reply from GMAT/MBA Admissions Expert
See All Featured Experts
Stacey Koprince
GMAT Instructor



Joined: 27 Dec 2006
Posts: 1899

Thanks given: 0
Thanked 285 times in 249 posts
Location: Montreal, Canada

GMAT Score: 780
PostMon Feb 26, 2007 11:57 pm
Nice job guys! Caps, when posting questions, please post the full text of the question (eg, for the first PS question, please post the answers). Choosing the best solving strategy is sometimes only possible when you know what the answers are.
_________________
Stacey Koprince
GMAT Instructor
Director of Online Community
Manhattan GMAT

Contributor to Beat The GMAT!

Learn more about me
Back to top
View user's profile Send private message
Display posts from previous:   

Post New Topic   Post Reply All times are GMT - 7 Hours
Page 1 of 1
 
Forum Index GMAT Math
Most Active Members in Last 30 Days
1. kstv 322 posts
2. shashank.ism 312 posts
3. harsh.champ 308 posts
4. gmatmachoman 256 posts
5. thephoenix 238 posts
See More Top Beat The GMAT Members
Most Active Experts in Last 30 Days
1. lunarpower
Manhattan GMAT Teacher 		97 posts
2. Stuart Kovinsky
Kaplan GMAT Teacher 		58 posts
3. Testluv
Kaplan GMAT Teacher 		51 posts
4. Lisa Anderson
Stacy Blackman Consulting 		49 posts
5. Bryant@VeritasPrep
Veritas Prep 		41 posts
See More Top Beat The GMAT Experts