Find the 20th term and the sum of the first 14 terms of this progression, 2, 5, 8, 11,.........?

Question

kropot72 · Answer

This is an arithmetic progression with the first term a = 2 and the common difference d = 3. The formula for finding the nth term of an AP is
$$n _{th}\ term = a+(n-1)d$$
To find the 20th term plug the values of a (2), n (20) and d (3) into the formula,

anonymous · Answer

Given progression, 2, 5, 8, 11,.........  is a arithmetic progression

Here First term (a) = 2

and Common difference (d) = 5 - 2 = 3

We know, nth term can be represented as, an = a + (n - 1)d

and sum of n terms = n/2{2a + (n - 1)d}

To find 20th term of the series

=> a20 = a + 19 d

= 2 + 19 * 3

= 2 + 57

= 59

=> 20th term = 59

Sum of first 14 terms = 14/2{2 * 2 + (14 - 1) * 3}

= 7{4 + 39}

= 7 * 43

= 301

=> Sum of first 14 terms = 301.

goformit100 · Answer

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