Boating Probabilities..

A boat's crew consists of 8 men , 3 of whom can only row on one side and 2 only on the other . Find the number of ways in which the crew can be arranged.

Note that : Only 4 men can be seated on a particular side.


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The answer is 1728.

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3 solutions

It is not mentioned in the question that only 4 can row on one side....

Vighnesh Raut - 6 years, 3 months ago

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@Vighnesh Raut it is basic common sense and understood that if the weight balance of the crew is not balanced. then the boat might topple over on one side..

Harshvardhan Mehta - 6 years, 3 months ago

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It must be mentioned in the question that only 4 can row on one side. Did you create this question? Though I got this correct ,this question is not worded properly.:(

Nihar Mahajan - 6 years, 3 months ago

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@Nihar Mahajan In future, if you spot any errors with a problem, you can “report” it by selecting the “dot dot dot” menu in the lower right corner.

Calvin Lin Staff - 6 years, 3 months ago

Its a combinatorics problem where we must count all the possible ways until it is not mentioned

Vighnesh Raut - 6 years, 3 months ago

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@Vighnesh Raut ohk i'll mention it alright..!!!

Harshvardhan Mehta - 6 years, 3 months ago

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@Harshvardhan Mehta Thank you boss..

Vighnesh Raut - 3 years, 7 months ago

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@Vighnesh Raut @Vighnesh Raut glad to see you still visit here.

Harshvardhan Mehta - 3 years, 5 months ago

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@Harshvardhan Mehta i m a regular member. XD

Vighnesh Raut - 3 years, 5 months ago

How can we click the picture of solution and post?

Sarthak Shiv - 3 years, 7 months ago

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Copy paste??

Sarthak Shiv - 3 years, 7 months ago

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On desktop, you can upload an image - Click on the third icon from the left in the formatting toolbar:

Currently, there is no easy way to do so on the apps.

Calvin Lin Staff - 3 years, 7 months ago
Nicola Mignoni
May 7, 2018

Side A

There are 4 4 seats and 3 3 men must occupies them. The number of ways we can arrange them is 4 ! ( 4 3 ) ! = ( 4 3 ) 3 ! \frac{4!}{(4-3)!}=\binom{4}{3}3! (non-repeated ordered disposition)

Side B

There are 4 4 seats and 2 2 men must occupies them. The number of ways we can arrange them is 4 ! ( 4 2 ) ! = ( 4 2 ) 2 ! \frac{4!}{(4-2)!}=\binom{4}{2}2! (non-repeated ordered disposition)

There are 3 3 men and 3 3 seats left. The number of ways we can arrange them is 3 ! 3! .

Hence, there are N N possible disposition for the crew, namely

N = ( 4 3 ) ( 4 2 ) 2 ! 3 ! 2 = 1728 \displaystyle N=\binom{4}{3} \binom{4}{2} 2! \cdot 3!^2=\boxed{1728}

Miki Moningkai
Feb 14, 2015

sides for 5 women are pre-decided of the remaining 3, there are 3c1 = 3 ways to choose the woman for the bow side the remaining 2 automatically get allocated to the stroke side.

now, on each side, there can be 4! arrangements of the women, so total # of ways = 3 4! 4! = 1728 <-----------

QED

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