Hey everyone(adsbygoogle = window.adsbygoogle || []).push({});

I had difficulties while solving this problem in probability.

We have 4 similar boxes, and 20 similar balls.

How many possible ways we can put those balls on those boxes, knowing that

-the first box contains 3 balls

- the second box contains 4 balls

- the third box contains 6 balls

- and the fourth box contains 7 balls

What I did, is since we have 4 boxes, it's going to be 4!

in the first box it's 3! and second, third and fourth i also 4!*6!*7!

So is the number of ways we can diperse those balls: 4!*4!*6!*7!

???

The secong problem stats:

How many 3-digits numbers we have that that contains 2 similar digits!

For this one, I have NO clue how to proceed.

Thanks for your help!

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# A question in probability

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