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12 Aug 2022, 07:13
Kudos
Bookmarks
Its a binomial situation ,
since the P(having Boy or girl ) is independent and its 1/2 we can use the formula
P(E) = nCr P(success)^r P(failure)^(n-r)
= 6C4 (1/2)^4 (1/2)^2
= 15/64
since the P(having Boy or girl ) is independent and its 1/2 we can use the formula
P(E) = nCr P(success)^r P(failure)^(n-r)
= 6C4 (1/2)^4 (1/2)^2
= 15/64
14 Aug 2022, 07:39
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KarishmaB
Bunuel
chetan2u
GMATinsight
why does it have to be a case of ordering? question didn’t say anything about order...it simply asked if there are 4 boys and 2 girls...
if we consider the cases, as-
6 Girls
5 girls and 1 boy
4 girls and 2 boys
3 girls and 3 boys
2 girls and 4 boys
1 girl and 5 boys
So there are 7 cases...and 4 boys can happen only in one way...
so probability : 1/7
what's wrong with this reasoning?
Posted from my mobile device
Bunuel
chetan2u
GMATinsight
why does it have to be a case of ordering? question didn’t say anything about order...it simply asked if there are 4 boys and 2 girls...
if we consider the cases, as-
6 Girls
5 girls and 1 boy
4 girls and 2 boys
3 girls and 3 boys
2 girls and 4 boys
1 girl and 5 boys
So there are 7 cases...and 4 boys can happen only in one way...
so probability : 1/7
what's wrong with this reasoning?
Posted from my mobile device
16 Aug 2022, 00:27
Kudos
Bookmarks
Mugdho
KarishmaB
Bunuel
chetan2u
GMATinsight
why does it have to be a case of ordering? question didn’t say anything about order...it simply asked if there are 4 boys and 2 girls...
if we consider the cases, as-
6 Girls
5 girls and 1 boy
4 girls and 2 boys
3 girls and 3 boys
2 girls and 4 boys
1 girl and 5 boys
So there are 7 cases...and 4 boys can happen only in one way...
so probability : 1/7
what's wrong with this reasoning?
Posted from my mobile device
Bunuel
chetan2u
GMATinsight
why does it have to be a case of ordering? question didn’t say anything about order...it simply asked if there are 4 boys and 2 girls...
if we consider the cases, as-
6 Girls
5 girls and 1 boy
4 girls and 2 boys
3 girls and 3 boys
2 girls and 4 boys
1 girl and 5 boys
So there are 7 cases...and 4 boys can happen only in one way...
so probability : 1/7
what's wrong with this reasoning?
Posted from my mobile device
Take a parallel example: You have a pair of dice. Is the probability of getting a sum of 2 on the throw the same as the probability of getting a sum of say, 6?
To get a sum of 2, you need both dice to show exactly 1. The probability of that is 1/6 * 1/6.
But to get a 6, one die could show 1 and the other 5 or one die could show 2 and the other 4 or both die could show 3 each. So probability of getting a sum of 6 is higher, right? It can happen in multiple ways.
Similarly, is the probability of getting all 6 girls same as the probability of getting 2 girls and 4 boys? No.
To get all 6 girls, you need to get a girl every time which means GGGGGG which gives (1/2)*(1/2)*(1/2)*(1/2)*(1/2)*(1/2).
But we can obtain 2 girls and 4 boys in many ways: GGBBBB, GBGBBB, BBGBBG, BBBBGG etc. So the probability of both is not the same. Then 1/7 doesn't work, right?
