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A family with 1 mother, 1 father, and 3 children sit in a car with 2

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A family with 1 mother, 1 father, and 3 children sit in a car with 2  [#permalink]

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New post 30 May 2016, 13:20
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  45% (medium)

Question Stats:

57% (00:57) correct 43% (00:44) wrong based on 133 sessions

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A family with 1 mother, 1 father, and 3 children sit in a car with 2 front seats and 3 back seats. If the mother drives with a child in the front, and the father sits in the back with the other two children, how many seating arrangements are possible?

(A) 3
(B) 4
(C) 6
(D) 12
(E) 18

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A family with 1 mother, 1 father, and 3 children sit in a car with 2  [#permalink]

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New post 30 May 2016, 14:45
I wasn't sure if the order of the way children are arranged matters in this question. Since children were mentioned as one (imagine we have 1 RED marble, 1 BLUE and 3 GREEN) and the front two seats are already determined, then there are 3 ways how the father can be seated in the back seat with regards to his children:

F C C
C F C
C C F

But if the order matters, then my solution doesn't hold. I am looking forward to discover the actual solution! :)
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Re: A family with 1 mother, 1 father, and 3 children sit in a car with 2  [#permalink]

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New post 30 May 2016, 17:58
In the front seat we have 3 possibilities of children. (C1 or C2 or C3)
In the back seat we have (2!*1)*3 = 6 possibilities ( C1,C2,F / C2,C1,F / C1,F,C2 / C2,F,C1 / F,C1,C2 / F,C2,C1 -> IF C3 is in front seat)
So, 6*3 = 18 (try to figure out to change the possibilities of sitting back the C3 child in the place of C1 or C2 and do the 6 possibilities again and again).

Or, another way to see:
Looking into the back seat:
( C1,C2,F / C2,C1,F / C1,F,C2 / C2,F,C1 / F,C1,C2 / F,C2,C1) = 6
or +
( C3,C2,F / C2,C3,F / C3,F,C2 / C2,F,C3 / F,C3,C2 / F,C2,C3) = 6
or +
( C1,C3,F / C3,C1,F / C1,F,C3 / C3,F,C1 / F,C1,C3 / F,C3,C1) = 6
-------
18
Letter E :-D
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Re: A family with 1 mother, 1 father, and 3 children sit in a car with 2  [#permalink]

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New post 31 May 2016, 05:32
1
Seat of mother is fixed
one child is in the front but we don't know which one.
So lets consider child one is in the front, so we have 3! = 6 arrangements in the backseat
then consider child two is in the front, again we have 3! = 6 arrangements
And the same for the last one. 6*3 = 18, hence E
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Re: A family with 1 mother, 1 father, and 3 children sit in a car with 2  [#permalink]

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New post 31 May 2016, 06:04
1
fantaisie wrote:
I wasn't sure if the order of the way children are arranged matters in this question. Since children were mentioned as one (imagine we have 1 RED marble, 1 BLUE and 3 GREEN) and the front two seats are already determined, then there are 3 ways how the father can be seated in the back seat with regards to his children:

F C C
C F C
C C F

But if the order matters, then my solution doesn't hold. I am looking forward to discover the actual solution! :)


Hi,

Your answer would have been correct had we been looking at identical things, the way you have mentioned about RED marble..
But here the order of chidren will also matter as these are different identities..
so 3*3!... 3! is the way these 3 kids can be arranged within themselves
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Re: A family with 1 mother, 1 father, and 3 children sit in a car with 2  [#permalink]

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New post 12 Jun 2017, 03:38
[quote="chetan2u"]

If the question asks about number of arrangements then why are we not considering the mothers seat combination ?


We got 18 but there are 3 combinations of either of 3 child sitting with the mother, Then we the answer is not 21?
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Re: A family with 1 mother, 1 father, and 3 children sit in a car with 2  [#permalink]

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New post 14 Jun 2017, 16:20
1
Bunuel wrote:
A family with 1 mother, 1 father, and 3 children sit in a car with 2 front seats and 3 back seats. If the mother drives with a child in the front, and the father sits in the back with the other two children, how many seating arrangements are possible?

(A) 3
(B) 4
(C) 6
(D) 12
(E) 18


We can let F be the father, M be the mother, and A, B, and C be the 3 children. We are given that the mother must occupy the driver’s seat and one of the children is sitting in the front.

So, let’s assume that M and A are sitting in the front; this leaves F, B, and C sitting in the back. The front row seats are fixed since M must be at the driver’s seat, but the back row seats are not. If F, B, and C are sitting in the back, there are 3! = 6 ways to occupy the back row seats.

Similarly, if M and B are sitting in the front and F, A, and C are sitting in the back, there will be also 6 ways to occupy the back row seats. Lastly, if M and C are sitting in the front and F, A, and B are sitting in the back, there will be another 6 ways to occupy the back row seats.

Thus the total number of seating arrangements is 6 + 6 + 6 = 18.

Answer: E
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Re: A family with 1 mother, 1 father, and 3 children sit in a car with 2  [#permalink]

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New post 19 Aug 2018, 09:41
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Re: A family with 1 mother, 1 father, and 3 children sit in a car with 2 &nbs [#permalink] 19 Aug 2018, 09:41
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