3 years ago

A teacher has 21 red pens. If the ratio of red pens to blue pens she owned was 3:1 , how many pens did she have total?

Mathematics

1 answer:

Kobotan [32]3 years ago

5 0

21/3 is 7 so there are 7 pens for every 1 ratio
7 x 1 = 7
21+7 = 28

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If an urn has 5 white balls 10 red balls what is the probability that 5 randomly selected balls contain exactly 3 white balls?

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Answer:

0.15

Step-by-step explanation:

Without Mincing words let us dive straight into the solution to the question above. We are given the following information which is going to aid in solving this particular question.

====> It is given, that there are 5 white balls and 10 red balls. Hence, the number of the total balls = 5 white balls + 10 red balls = 15 balls.

Therefore, the probability that 5 randomly selected balls contain exactly 3 white balls = $\left[\begin{array}{ccc}5\\3\end{array}\right]$ × $\left[\begin{array}{ccc}10\\2&\end{array}\right]$ ÷ $\left[\begin{array}{ccc}15\\3\\\end{array}\right]$ = 450 ÷ 3003 = 0.15