Answer: The required number of ninths needed is 3.
Step-by-step explanation: We are given to find the number of ninths that will after combining together make the amount as [tex]\dfrac{1}{3}.[/tex]
Let, 'n' be the required number of ninths.
Then, according to the given information, we have
[tex]n\times\dfrac{1}{9}=\dfrac{1}{3}\\\\\\\Rightarrow n=9\times \dfrac{1}{3}\\\\\\\Rightarrow n=3.[/tex]
Therefore, required number of ninth needed is 3.
Thus, the answer is 3.