It is currently 19 Oct 2017, 18:26

### 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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# Is xy<15? 1) x<3 2) y<5

Author Message
TAGS:

### Hide Tags

Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 4135

Kudos [?]: 2893 [0], given: 0

GPA: 3.82
Is xy<15? 1) x<3 2) y<5 [#permalink]

### Show Tags

03 Oct 2017, 01:37
Expert's post
1
This post was
BOOKMARKED
00:00

Difficulty:

25% (medium)

Question Stats:

68% (00:20) correct 32% (00:21) wrong based on 28 sessions

### HideShow timer Statistics

[GMAT math practice question]

Is xy<15?

1) x<3
2) y<5
[Reveal] Spoiler: OA

_________________

MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
Find a 10% off coupon code for GMAT Club members.
“Receive 5 Math Questions & Solutions Daily”
Unlimited Access to over 120 free video lessons - try it yourself

Kudos [?]: 2893 [0], given: 0

Senior Manager
Joined: 25 Feb 2013
Posts: 407

Kudos [?]: 174 [0], given: 31

Location: India
GPA: 3.82
Re: Is xy<15? 1) x<3 2) y<5 [#permalink]

### Show Tags

03 Oct 2017, 02:12
MathRevolution wrote:
[GMAT math practice question]

Is xy<15?

1) x<3
2) y<5

Statement 1: no value of $$y$$ is given. Insufficient

Statement 2: no value of $$x$$ is given. Insufficient

Combining 1 & 2, if $$x=2$$, $$y=4$$, then $$xy=8<15$$ but if $$x=-10$$, $$y=-2$$, then $$xy=20>15$$. Hence Insufficient

Option E

Kudos [?]: 174 [0], given: 31

Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 4135

Kudos [?]: 2893 [0], given: 0

GPA: 3.82
Re: Is xy<15? 1) x<3 2) y<5 [#permalink]

### Show Tags

05 Oct 2017, 03:12
=>

Forget conventional ways of solving math questions. In DS, VA (Variable Approach) method is the easiest and quickest way to find the answer without actually solving the problem. Remember that equal number of variables and independent equations ensures a solution.

There are 2 variables and 0 equation. Therefore, C is most likely to be the answer.

Conditin 1) & 2)
x = 1, y = 2 ➔ xy = 2 < 15 : Yes
x = -4, y = -4 ➔ xy = 16 > 16 : No

Therefore, unlike our expectation, E is the answer.

Normally for cases where we need 2 more equations, such as original conditions with 2 variables, or 3 variables and 1 equation, or 4 variables and 2 equations, we have 1 equation each in both con 1) and con 2). Therefore, C has a high chance of being the answer, which is why we attempt to solve the question using con 1) and con 2) together. Here, there is 70% chance that C is the answer, while E has 25% chance. These two are the key questions. In case of common mistake type 3,4, the answer may be from A, B or D but there is only 5% chance. Since C is most likely to be the answer according to DS definition, we solve the question assuming C would be our answer hence using con 1) and con 2) together. (It saves us time). Obviously, there may be cases where the answer is A, B, D or E.

Ans: E
_________________

MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
Find a 10% off coupon code for GMAT Club members.
“Receive 5 Math Questions & Solutions Daily”
Unlimited Access to over 120 free video lessons - try it yourself

Kudos [?]: 2893 [0], given: 0

Re: Is xy<15? 1) x<3 2) y<5   [#permalink] 05 Oct 2017, 03:12
Display posts from previous: Sort by