 It is currently 03 Jul 2020, 14:18

# The 4th of July - ### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

#### Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here. # If the sum of two numbers is known, which of the following  Question banks Downloads My Bookmarks Reviews Important topics
Author Message
TAGS:
Founder  Joined: 18 Apr 2015
Posts: 11932
Followers: 250

Kudos [?]: 2967 , given: 11171

If the sum of two numbers is known, which of the following [#permalink]
Expert's post 00:00

Question Stats: 50% (01:29) correct 50% (00:52) wrong based on 4 sessions
If the sum of two numbers is known, which of the following is NOT sufficient to determine the values of the two numbers?

(A) One number is greater than the other.

(B) The cube of one number is 8.

(C) The product of the two numbers is 8.

(D) The difference between the two numbers ·is 2.

(E) One number is half the other.

Kudos for the right answer and explanation
[Reveal] Spoiler: OA

_________________

Need Practice? 20 Free GRE Quant Tests available for free with 20 Kudos
GRE Prep Club Members of the Month: Each member of the month will get three months free access of GRE Prep Club tests. Intern Joined: 23 Jun 2020
Posts: 24
Followers: 1

Kudos [?]: 16  , given: 1

Re: If the sum of two numbers is known, which of the following [#permalink]
1
KUDOS
Lets use the elimination method:

a) One number is greater than the other. If we don't know by how much it is different we can't determine the numbers. If the sum is 15 the two numbers can be 7 and 8 or 3 and 12, thus just knowing that one is larger than the other won't help us determine the identity of the numbers

b) The cube of one number is 8. This tells us that one of the numbers is 2 (2^3 = 8). We can then determine the second number by doing sum-2

c) The product of the two numbers is 8. Two numbers a and b when multiplied equal to 8 (a*b=8). One of the numbers (lets say a) can be expressed using the other number a=8/b. Then sum (which is just a number that would have been given to us) equals b+(8/b) .
The b can be expressed as b^2/b to add to 8/b and yield (b^2+8)/b = sum
Then since sum is a number we can multiply both sides of the equation by b to get: b^2+8 = sum*b
Subtract sum*b from both sides to get yourself a quadratic b^2 - sum*b + 8 =0
You can solve this for b and then figure out a

d) The difference between the two numbers ·is 2. This tells us that the two numbers can be expressed as x and x+2. Thus sum = x+ (x+2). We can determine x (one of the numbers) and then add 2 to determine the second number.

e) One number is half the other. If one number (a) is half of the other number (b), we then know that a=0.5b. Thus the total sum of a+b = 1b+0.5b =1.5b. Then the sum can be divided by 1.5 to determine b, and then do sum -b to determine the other number

Thus only A is not a sufficient qualifying statement to determine the values of the two numbers
_________________

If you found my explanation useful, please do not hesitate to click the karma button Manager  Joined: 10 Feb 2020
Posts: 186
Followers: 1

Kudos [?]: 46 , given: 110

Re: If the sum of two numbers is known, which of the following [#permalink]
Well, if we dont know even a single number how can we come up with solution? Say for example option C says "The product of the two numbers is 8." it could be 2*4=8 or 8*1=8..so there are multiple possibilities and this is the same reason in comparison questions we mark D s option. This is a very confusing question
_________________

Ever Tried? Ever Failed? No Matter. Try Again. Fail Again. Fail Better!! Re: If the sum of two numbers is known, which of the following   [#permalink] 24 Jun 2020, 17:55
Display posts from previous: Sort by

# If the sum of two numbers is known, which of the following  Question banks Downloads My Bookmarks Reviews Important topics Powered by phpBB © phpBB Group Kindly note that the GRE® test is a registered trademark of the Educational Testing Service®, and this site has neither been reviewed nor endorsed by ETS®.