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# There are four blue marbles, an unknown number of red (r marbles, and six yellow marbles in a bag. which expression represents the probability of randomly selecting a blue marble, replacing it, and then randomly selecting a red marble?

There are a total of $4+r+6$ marbles in the bag The probability of choosing a blue is $\frac{4}{10+r}$ The probability of choosing a red is $\frac{r}{10+r}$ The probability of choosing a blue, replacing it, and then a red is $\frac{4}{10+r}$×$\frac{r}{10+r}$ = $\frac{4r}{100+20r+ r^{2} }$