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

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Math Expert
Joined: 02 Sep 2009
Posts: 57155
The number of connections C that can be made through a switchboard to  [#permalink]

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03 Aug 2019, 23:24
1
00:00

Difficulty:

15% (low)

Question Stats:

100% (01:21) correct 0% (00:00) wrong based on 11 sessions

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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

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Joined: 11 Jul 2018
Posts: 4
Re: The number of connections C that can be made through a switchboard to  [#permalink]

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03 Aug 2019, 23:34
B: 245

(30x29/2)-(20×19/2)

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Re: The number of connections C that can be made through a switchboard to   [#permalink] 03 Aug 2019, 23:34
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