Cat says Meo Meo.. :D !!!

Lets consider the sample space or all possible outcomes : (f,f),(m,m),(f,m),(m.f) where f and m denote female and male. Since we are told that at least one of the kitten is female, we can strike off (m,m). The question ask what is the probability that the other is a boy which only can happen if it is (f,m) or (m,f) out of the other 3 combinations. Hencee, answer is 2/3.

Consider the following possible scenarios, each having $\frac{1}{4}$ chance of occuring.

Calv - M, Clava - M

Calv - F, Clava - M

Calv - M, Clava - F

Calv - F, Clava - F

Now consider the cases where at least one of them is female.

Calv - F, Clava - M

Calv - M, Clava - F

Calv - F, Clava - F

In those three scenarios, the remaining kitten is female in $1$ scenario, and the remaining kitten is male in $2$ scenarios.

So the answer is $\frac{2}{3}=0.666... \approx \boxed{0.67}$ .

answer is 2/3

which can be written in decimals as 0.66666666.... or

0.67 (approximately)