The number of ways of giving 20 distinct oranges to 3 children such that each child gets at least one orange is ___________.
Answer (integer)
3483638676
Solution
<li><p><strong>Total ways without any restrictions :</strong>
<br/><br/>There are $3^{20}$ ways to distribute the oranges to the 3 children.</p>
</li>
<li><p><strong>Number of ways one child receives no orange :</strong>
<br/><br/>Choose 1 child out of the 3 to not receive any orange in ${ }^3 C_1 = 3$ ways. Distribute 20 oranges to the remaining 2 children in $2^{20}$ ways. However, we've included the scenarios where the 2 children each get all the oranges. So, we subtract the 2 ways where one of the two remaining children gets all the oranges.
$ { }^3 C_1(2^{20} - 2) $</p>
</li>
<li><p><strong>Number of ways two children receive no orange :</strong>
<br/><br/>Choose 2 children out of the 3 to not receive any oranges in ${ }^3 C_2 = 3$ ways. The third child will receive all 20 oranges in $1^{20} = 1$ way.
$ { }^3 C_2 \times 1^{20} = 3 $</p>
</li>
</ol>
<br/>Number of ways <br/><br/>$=$ Total $-($ One child receive no orange + two child receive no orange)
<br/><br/>$$
\begin{aligned}
& =3^{20}-\left({ }^3 C_1\left(2^{20}-2\right)+{ }^3 C_2 1^{20}\right) \\\\
& =3483638676
\end{aligned}
$$
About this question
Subject: Mathematics · Chapter: Permutations and Combinations · Topic: Fundamental Counting Principle
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