NEW HERE? LEARN MORE
closeclose
Last visit was: 26 Apr 2024, 18:53 It is currently 26 Apr 2024, 18:53
Decision Tracker
My Rewards
New posts
New comers' posts

Close
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
Your Progress

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.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel

If ten parallel lines were intersected by another nine parallel lines

SORT BY:
Date
Kudos
Tags:
Find Similar Topics 
Show Tags
Hide Tags
User avatar
L
Bunuel
Math Expert
Joined: 02 Sep 2009
Posts: 92948
Own Kudos [?]: 619247 [10]
Given Kudos: 81609
Send PM
CAT Tests Forum Quiz Mode
If ten parallel lines were intersected by another nine parallel lines [#permalink] New post   19 Nov 2020, 03:15
1
Kudos
9
Bookmarks
Expert Reply
00:00
A
B
C
D
E

Difficulty:

75% (hard)

Question Stats:

35% (01:26) correct 65% (01:54) wrong based on 57 sessions
Hide Show timer Statistics
If ten parallel lines were intersected by another nine parallel lines, then how many parallelograms are formed?

A. 72
B. 1008
C. 1320
D. 1520
E. 1620
ShowHide Answer
Official Answer
E
avatar
B
parth2424
Intern
Intern
Joined: 11 Oct 2020
Posts: 38
Own Kudos [?]: 8 [0]
Given Kudos: 122
Send PM
Re: If ten parallel lines were intersected by another nine parallel lines [#permalink] New post   19 Nov 2020, 04:13
B - its an educated guess. Please explain how

Posted from my mobile device
User avatar
L
Archit3110
GMAT Club Legend
GMAT Club Legend
Joined: 18 Aug 2017
Status:You learn more from failure than from success.
Posts: 8020
Own Kudos [?]: 4098 [1]
Given Kudos: 242
Location: India
Concentration: Sustainability, Marketing
GMAT Focus 1:
545 Q79 V79 DI73
GPA: 4
WE:Marketing (Energy and Utilities)
Send PM
GMAT ToolKit User CAT Tests
Re: If ten parallel lines were intersected by another nine parallel lines [#permalink] New post   19 Nov 2020, 04:47
1
Kudos
Bunuel wrote:
If ten parallel lines were intersected by another nine parallel lines, then how many parallelograms are formed?

A. 72
B. 1008
C. 1320
D. 1520
E. 1620


total possible pairs
9c2 *8c2 ; 1008
option B
avatar
P
ananya3
Current Student
Joined: 05 Oct 2018
Posts: 108
Own Kudos [?]: 109 [3]
Given Kudos: 152
Location: India
Schools: Fuqua '24 Haas '24 ISB '23 Johnson '24 Kelley '24 Kenan-Flagler '24 McDonough '24 NUS Ross '24 Tepper '24 Tuck '24 Rotman '24 (A)
GMAT 1: 700 Q49 V36
GPA: 3.87
Send PM
GMAT ToolKit User
Re: If ten parallel lines were intersected by another nine parallel lines [#permalink] New post   19 Nov 2020, 23:22
2
Kudos
1
Bookmarks
IMO E

a parallelogram can be formed by 2 pairs of parallel lines that would intersect to form the two pairs of parallel sides of the parallelogram
therefore we need to select 2 lines from the set of 10 parallel lines = 10C2
and the other two lines from the set of 9 parallel lines = 9C2

=> total possible combinations = 10C2 * 9C2 = 1620
User avatar
G
ThatDudeKnows
Tutor
Joined: 11 May 2022
Posts: 1092
Own Kudos [?]: 697 [1]
Given Kudos: 81
Send PM
Re: If ten parallel lines were intersected by another nine parallel lines [#permalink] New post   16 Jul 2022, 16:41
1
Kudos
Expert Reply
Bunuel wrote:
If ten parallel lines were intersected by another nine parallel lines, then how many parallelograms are formed?

A. 72
B. 1008
C. 1320
D. 1520
E. 1620


We need any two lines from the set of ten. We have 10 choices for the first and 9 for the second. 10*9 = 90. AB is the same as BA, so we need to divide by 2. 90/2 = 45.

We need two lines from the set of nine. We have 9 choices for the first and 8 for the second. 9*8 = 72. AB is the same as BA, so we need to divide by 2. 72/2 = 36.

36*45 = 1620

Answer choice E.
GMAT Club Bot
gmatclubot
Re: If ten parallel lines were intersected by another nine parallel lines [#permalink]
16 Jul 2022, 16:41
Moderators:
Bunuel
Math Expert
92948 posts
yashikaaggarwal
Senior Moderator - Masters Forum
3137 posts

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne
Main navigation
GMAT Resources
Partners
MBA Resources
www.gmac.com|www.mba.com | | GMAT Club Rules | Terms and Conditions