BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Is there any better approach to solve this Simple Question?

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Senior | Next Rank: 100 Posts
Posts: 52
Joined: Mon Jan 14, 2008 7:46 pm
Thanked: 3 times

Is there any better approach to solve this Simple Question?

by gmataspirant » Sun Jun 01, 2008 5:47 pm
Hey Guys,

Is there any short cut method availalbe to answer the following simple question ?

What is the greatest integer that is a sum of four different prime numbers, each less than 30 ?

A 67
B 88
C 98
D 104
E 126

I narrowed down the options to A,B,C,D and ignored option E as it is over 120. Answered the question by summing up different prime numbers which are less than 30. I am sure that there must be a smarter approach to solve this question. :oops:
Never GiveUp For Any Reason
Top
Source: — Problem Solving |
Master | Next Rank: 500 Posts
Posts: 127
Joined: Sat Apr 19, 2008 1:02 am
Thanked: 12 times

by jasonc » Sun Jun 01, 2008 6:18 pm
not sure how to do it faster... but even if you just sum up the 4 primes, it shouldn't take more than 1 min.

count down from 30 to find the highest 4 primes, sum those = answer.
29, 23, 19, 17=88
I beat the GMAT! 760 (Q49/V44)
Top
Junior | Next Rank: 30 Posts
Posts: 14
Joined: Fri Apr 04, 2008 11:28 pm

by sasi78 » Sun Jun 01, 2008 7:07 pm
I think, no need to use POE for this kind of problems. Solving directly is the simple & less time consuming way.
Top
Master | Next Rank: 500 Posts
Posts: 106
Joined: Sun Feb 17, 2008 10:09 pm
Thanked: 3 times

by ksh » Mon Jun 02, 2008 3:39 am
I think you have solved the right way.

It is difficult to deduce any formulae for it. Its better to count n add 29+23+19+17=88.

Cheer up
Top
User avatar
GMAT Instructor
Posts: 85
Joined: Thu May 01, 2008 12:56 pm
Location: Salt Lake City, UT
Thanked: 24 times
GMAT Score:750+

by VP_RedSoxFan » Mon Jun 02, 2008 6:35 am
Sometimes we can out-think ourselves when trying to come up with a neat "trick". As has been mentioned, take the 45 seconds or so and focus energies on getting the 4 greatest prime numbers less than 30 accurately.
Ryan S.
| GMAT Instructor |
Elite GMAT Preparation and Admissions Consulting
www.VeritasPrep.com

Learn more about me
Top

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 2623
Joined: Mon Jun 02, 2008 3:17 am
Location: Montreal
Thanked: 1090 times
Followed by:355 members
GMAT Score:780

by Ian Stewart » Mon Jun 02, 2008 4:01 pm
There's no formula for finding primes; the only reliable way to do this problem is to locate the four largest primes less than 30 and add them up. You really should know all primes up to at least 40, and if you do, this question should only take 30 seconds- you only need to add four small numbers. Otherwise, it still should only take a minute.
Top
Post new topic Post Reply
• Page 1 of 1