Find all School-related info fast with the new School-Specific MBA Forum

 It is currently 04 Jul 2015, 06:48

### 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

# 1) there is a square in the XY co-ordinate system with its

Author Message
TAGS:
Senior Manager
Joined: 21 Aug 2003
Posts: 258
Location: Bangalore
Followers: 1

Kudos [?]: 4 [0], given: 0

1) there is a square in the XY co-ordinate system with its [#permalink]  25 Sep 2003, 06:58
1) there is a square in the XY co-ordinate system with its vertices
as {(1,1), (1,-1), (-1,-1), (-1,1)}. What is the probability that a
point picked at random within this square region will satisfy the
equation x^2+y^2<1?

2) if 2 numbers are chosen from 0-9 inclusive, what is the
probability that its product will be even?
SVP
Joined: 03 Feb 2003
Posts: 1607
Followers: 7

Kudos [?]: 84 [0], given: 0

(1) X^2+Y^2<1 is an origin-center circle, its radius being 1.

So, employ the geometrical sense of the probability: the favorable area/the total area

FA=pi
TA=4

P=pi/4

(2) P(an even product of the two)=1-P(odd,odd)=1-[5/10*4/9]=1-2/9=7/9
Manager
Joined: 15 Sep 2003
Posts: 74
Location: california
Followers: 1

Kudos [?]: 6 [0], given: 0

i agree with stolyar
Intern
Joined: 11 Jul 2003
Posts: 28
Followers: 0

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

1. Please can u explain how the equation is the origin of a circle. I do not understand.

2. I do not understand why 1-p(O,O) is used, as we need to select only one even number, the second number can be either odd or even, as we nedd the product ot be even.

so P(even #)=5/10 * P(any other #)9/9 = 0.5

am i right ?
SVP
Joined: 03 Feb 2003
Posts: 1607
Followers: 7

Kudos [?]: 84 [0], given: 0

(1) the equation of an origin-centered circumference is x^2+y^2=R^2, a direct use of the Pythagorean theorem.

(2) all the possible combinations for a product are EE, EO, OE, OO. The first three gives an even product; the last one gives an odd one. So, it is correct to calculate probabilities for each of the first three cases and add them up, but it is more concise and elegant to calculate the probability of the opposite case and subtract it from 1.
Intern
Joined: 24 Sep 2003
Posts: 38
Location: India
Followers: 1

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

1. Because there is no term having x and y in the equation of circle. A general equation of circle is (X-x)**2 + (Y-y)**2=R**2. That's why it's circle having centre as origin and radius is 1.

2. There should be atleast one number should be even out of 2, if there multiplication is even. So if deduct probability of multiplication of (odd,odd) from total probability (i.e. 1), we can get desired probability.
Senior Manager
Joined: 21 Aug 2003
Posts: 258
Location: Bangalore
Followers: 1

Kudos [?]: 4 [0], given: 0

-vicky
Intern
Joined: 11 Jul 2003
Posts: 28
Followers: 0

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

THANKS [#permalink]  26 Sep 2003, 12:20
Thanks for the explanations.
THANKS   [#permalink] 26 Sep 2003, 12:20
Similar topics Replies Last post
Similar
Topics:
In the XY coordinate system, if (a,b) and (a+3,b+k) are two 6 10 Mar 2008, 19:06
In the XY-coordinate system, if (a,b) and (a+3, b+ K) are 4 18 Jan 2008, 10:25
In the xy-coordinate system, if (a,b) and (a+3, b+k) are two 3 07 Oct 2006, 20:35
In the xy-coordinate system, rectangle ABCD is inscribed 1 04 May 2006, 08:06
In the xy coordinate system, if (a,b) and (a+3, b+k) are two 4 09 Nov 2005, 16:51
Display posts from previous: Sort by

# 1) there is a square in the XY co-ordinate system with its

 Powered by phpBB © phpBB Group and phpBB SEO Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.