Question

Find the sum of first 10th term of an ap whose the first term is 3 and 10th term is 39

Answer 1

Answer:

210

Step-by-step explanation:

a=3

t₁₀ = 39

=> 3 + (10-1)d = 39

=> 9d = 36

=> d = 36/9 = 4

d=4

Sₙ =(n/2)[2a+(n-1)d]

=>S₁₀ = (10/2)[2(3)+(10-1)4]

         = 5 [ 6+36]

        = 5*42

        = 210

Answer 2

Answer:

210

Step-by-step explanation:

we have,

a=3&

number of terms =10

a10 =100 (last term)

Sn=n/2(a+l)

10/ 2(3+39)

5(42)

210..