Question

Find the sum of the following AP 10 term is 5,9,13, ...​

Answer 1

Answer:

270

Step-by-step explanation:

sum of AP = n/2 [2a + (n+1)d]

here, n=10, a=5, d=9-5=4

S= 10/2(2×5 + (10+1)4)

= 5(10 + 44)

= 5(54)

= 270

Answer 2

Answer :-

a = 5

d = 9 - 5 = 4

We know the formula to find the nth term, that is :-

a(n) = a + (n -1) d

= 5 + (10-1) 4

= 5 + (9×4)

= 5 + 36

= 41

To find the sum of numbers of 5,9,13....41 (upto 10th term) we use the formula,

{n(n+1)}/2

= {41(41+1)}/2

= {41×42}/2

= 1722/2

= 861 (Answer).