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Hint: Since it is given that it is in A.P, start by finding the first term, common difference and form the equation of general term using these, after that put the value of n in the equation to obtain the answer.

Given series: $4,9,14,...$

Difference between the first and the second term is $5$, and the second and third term is also $5$.

Therefore, common difference in this series is $5$,

Now, applying the general term formula here,

We get,

${t_n} = 4 + \left( {n - 1} \right)5 = 5n - 1$

For $n = 11,{t_n} = 5\left( {11} \right) - 1 = 54$

Therefore,

Answer = 54

Note: In these questions, our first aim should be to form a generalized equation so that we can just put the value of the entity that is asked to get the answer.

Given series: $4,9,14,...$

Difference between the first and the second term is $5$, and the second and third term is also $5$.

Therefore, common difference in this series is $5$,

Now, applying the general term formula here,

We get,

${t_n} = 4 + \left( {n - 1} \right)5 = 5n - 1$

For $n = 11,{t_n} = 5\left( {11} \right) - 1 = 54$

Therefore,

Answer = 54

Note: In these questions, our first aim should be to form a generalized equation so that we can just put the value of the entity that is asked to get the answer.