Given:
A dice is rolled.
To find:
How many times a six-sided dice needs to be rolled to obtain the number 4 twenty times.
Solution:
We know that, if we roll a dice then the possible outcomes are 1, 2, 3, 4, 5, 6.
Total possible outcomes = 6
So, the probability of getting a 4 in one roll is:
[tex]P(4)=\dfrac{1}{6}[/tex]
Let n be the number of times the dice is rolled to obtain the number 4 twenty times. Then,
[tex]\dfrac{1}{6}\times n=20[/tex]
[tex]\dfrac{n}{6}=20[/tex]
[tex]n=20\times 6[/tex]
[tex]n=120[/tex]
Therefore, the correct option is C.
