Probability 4020

There are numbers from 1 to 20 in the hat. What is the probability that we will pull out from the hat:

a / one-digit number
b / prime number
c / number greater than 11
d / a number divisible by six
Thank you

Correct answer:

a =  0.45
b =  0.35
c =  0.45
d =  0.15

Step-by-step explanation:

$$\begin{gathered} n=20 \\ a=9/n=9/20=0.45 \end{gathered}$$

$$\begin{gathered} p_1=\{2,3,5,7,11,13,17\} \\ b=7/n=7/20=0.35 \end{gathered}$$

$c=9/n=9/20=0.45$

$$\begin{gathered} p_2=\{6,12,18\} \\ d=3/n=3/20=0.15 \end{gathered}$$

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