Question

What is the 30th number in the series 1,2,4,7,11,16....

Answer 1

Answer:

The 30th term of given sequence is 436.

Step-by-step explanation:

The given sequence is

1,2,4,7,11,16....

From these terms it is clear that the nth terms is the sum of (n-1)th term and (n-1).

$a_n=a_1+\sum {(n-1)}$

$a_n=a_1+\frac{(n-1)n}{2}$

Where a1 is equal to 1.

We have to find the 30th term of this sequence.

Put n=30.

$a_{30}=1+\frac{(30-1)30}{2}$

$a_{30}=1+29\times 15=436$

Therefore the 30th term of given sequence is 436.

Answer 2

Answer:

The 30th term of given sequence is 436.

Step-by-step explanation:

The given sequence is

1,2,4,7,11,16....

From these terms it is clear that the nth terms is the sum of (n-1)th term and (n-1).

$a_n=a_1+\sum {(n-1)}$

$a_n=a_1+\frac{(n-1)n}{2}$

Where a1 is equal to 1.

We have to find the 30th term of this sequence.

Put n=30.

$a_{30}=1+\frac{(30-1)30}{2}$

$a_{30}=1+29\times 15=436$

Therefore the 30th term of given sequence is 436.