7 boys and 7 girls

[talaangoshtari]

In how many ways can 7 boys and 7 girls sit in a row?

1. Boys and girls at alternate positions
2. No two boys sit together

I cannot understand the difference between 1 and 2

[theCEO]

In how many ways can 7 boys and 7 girls sit in a row?

1. Boys and girls at alternate positions
2. No two boys sit together

I cannot understand the difference between 1 and 2

1. Boys and girls at alternate positions
This means no boy can sit beside another boy and no girl can sit beside another girl

2. No two boys sit together
This means no boy can sit beside another boy however the girls can sit anywhere they want to sit.

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Hi talaangoshtari,

It would probably help if you drew some sketches of the possibilities...

We have 7 boys and 7 girls sitting in a row.

1st option: Boys and girls sit at alternate positions

We could have....

BGBGBGBGBGBGBG

or

GBGBGBGBGBGBGB

2nd option: No two boys sit together

We could have either of the options above, but we could ALSO have...

BGGBGBGBGBGBGB (notice the two girls sitting next to one another in the 2nd and 3rd spots)

GMAT assassins aren't born, they're made,
Rich

[nikhilgmat31]

Brent, Can you please solve this question.

Also please provide me a chapter to read Permutation,Combination & Probability.

I am very weak in these three concepts.