# Perm and comb Qs (1 Viewer)

#### Jojofelyx

##### Active Member
Should the rowing one simply be 8C5 ?
And the other question, B?

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#### laterz laterz

##### Active Member
Should the rowing one simply be 8C5 ?
And the other question, B?
8C5 seems right to me but I am bad at this topic so don't quote me

#### Jojofelyx

##### Active Member
8C5 seems right to me but I am bad at this topic so don't quote me

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#### vishnay

##### Active Member
$\bg_white P(x)=(x-c)^{2}Q(x)\\$
$\bg_white P'(x)=2(x-c)Q(x)+(x-c)^{2}Q'(x)\\$
$\bg_white P'(c)=0\\$
$\bg_white \therefore x=c\ \text{is a root of} \ P'(x)$

#### Jojofelyx

##### Active Member
$\bg_white P(x)=(x-c)^{2}Q(x)\\$
$\bg_white P'(x)=2(x-c)Q(x)+(x-c)^{2}Q'(x)\\$
$\bg_white P'(c)=0\\$
$\bg_white \therefore x=c\ \text{is a root of} \ P'(x)$
tysm

#### pikachu975

Should the rowing one simply be 8C5 ?
And the other question, B?
2nd one would be 7C5 to pick the males, then 1/2^5 for boys and 1/2^2 for girls = 21/128 (D)

Haven't done this in a while though, but it seemed like binomial probability

#### Jojofelyx

##### Active Member
2nd one would be 7C5 to pick the males, then 1/2^5 for boys and 1/2^2 for girls = 21/128 (D)

Haven't done this in a while though, but it seemed like binomial probability
Yeah thank you, I realised that I forgot to account for the combinations of boys and girls that could happen, not just the 1 particular set of 5B and 2G in that order.