Question

Thuy rolls a number cube 7 times. Which expression represents the probability of rolling a 4 exactly 2 times?

Answer 1

Hence, the probability of rolling a 4 exactly 2 times is:

`(1)/(6)* (1)/(6)* (5)/(6)* (5)/(6)* (5)/(6)* (5)/(6)* (5)/(6)=(5^5)/(6^7)`

Explanation:

It is given that:

Thuy rolls a number cube 7 times.

so the total outcomes are: 6.

Also it is asked to find the probability of rolling a 4 exactly 2 times.

So it could be done by the method that:

`(1)/(6)* (1)/(6)* (5)/(6)* (5)/(6)* (5)/(6)* (5)/(6)* (5)/(6)`

( where
`(1)/(6)` denotes the probability of rolling a 4 and
`(5)/(6)` denotes the probability of rolling a number other than 4 ).

Hence, the probability of rolling a 4 exactly 2 times is:

`(1)/(6)* (1)/(6)* (5)/(6)* (5)/(6)* (5)/(6)* (5)/(6)* (5)/(6)=(5^5)/(6^7)`