It is currently 17 Aug 2019, 18:32

### 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

# The number of connections C that can be made through a switc

Author Message
TAGS:
Founder
Joined: 18 Apr 2015
Posts: 7695
Followers: 142

Kudos [?]: 1585 [0], given: 6981

The number of connections C that can be made through a switc [#permalink]  31 Jul 2019, 02:31
Expert's post
00:00

Question Stats:

100% (00:36) correct 0% (00:00) wrong based on 3 sessions
The number of connections C that can be made through a switchboard to which T telephones are connected is given by the formula $$C=\frac{T(T-1)}{2}$$ . How many more connectIOns are possible with 30 telephones than with 20 telephones?

(A) 435

(B) 245

(C) 190

(D) 45

(E) 10
[Reveal] Spoiler: OA

_________________
Director
Joined: 07 Jan 2018
Posts: 669
Followers: 8

Kudos [?]: 641 [0], given: 88

Re: The number of connections C that can be made through a switc [#permalink]  06 Aug 2019, 09:28
Solve for C with T = 20
we get,

C = 20(19)/2
or, C = 10*19 = 190

Again solve for C but this time with T = 30
C = 30(29)/2
or, C = 15(29)
or, C = 435
The difference is 435 - 190 = 245
_________________

This is my response to the question and may be incorrect. Feel free to rectify any mistakes

Re: The number of connections C that can be made through a switc   [#permalink] 06 Aug 2019, 09:28
Display posts from previous: Sort by