The probability that all of the buttons are black when four buttons are picked at random from a which jar contains four black buttons and three, is 1/35.
<h3>What is probability of an event?</h3>
Probability of an event is the ratio of number of favorable outcome to the total number of outcome of that event.
A jar contains four black buttons and three brown buttons. The total number of buttons is,

The probability of picking a black button in the first attempt is,

Now, there is total 6 buttons remain in which 3 are black buttons. Thus, the probability of picking black button in second attempt is,

Similarly, for the third event,

For the fourth event,

The probability that all of them are black by the chain rule of probability,

Thus, the probability that all of the buttons are black when four buttons are picked at random from a which jar contains four black buttons and three, is 1/35.
Learn more about the probability here;
brainly.com/question/24756209
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