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# In a series of races, 10 toy cars are raced, 2 cars at a time. If each

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Math Expert
Joined: 02 Sep 2009
Posts: 58464
In a series of races, 10 toy cars are raced, 2 cars at a time. If each  [#permalink]

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07 Mar 2019, 03:02
00:00

Difficulty:

35% (medium)

Question Stats:

54% (01:01) correct 46% (01:17) wrong based on 26 sessions

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In a series of races, 10 toy cars are raced, 2 cars at a time. If each car must race each of the other cars exactly twice, how many races must be held?

A. 45
B. 90
C. 180
D. 200
E. 220

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Re: In a series of races, 10 toy cars are raced, 2 cars at a time. If each  [#permalink]

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07 Mar 2019, 06:26
Bunuel wrote:
In a series of races, 10 toy cars are raced, 2 cars at a time. If each car must race each of the other cars exactly twice, how many races must be held?

A. 45
B. 90
C. 180
D. 200
E. 220

total cars = 10
10c2*2 = 90
IMO B
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Joined: 20 Jul 2018
Posts: 13
Re: In a series of races, 10 toy cars are raced, 2 cars at a time. If each  [#permalink]

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08 Mar 2019, 11:27
Total pool of car = 10 cars
2 cars compete each other hence group of 2 cars ..group=combination problem it is.

hence 10C2=45

now this will happen twice(i.e. each car must compete with other car twice) , multiply 45 by 2 =90

Therefore option 'B' is correct.
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Re: In a series of races, 10 toy cars are raced, 2 cars at a time. If each   [#permalink] 08 Mar 2019, 11:27
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