Question

What is the sum of a 10–term arithmetic sequence where the first term is 3 and the last term is 75?
Answer

Answer 1

sum 'S' of an AP upto 'n' where the first term 'a' and the last term 'l' is given:
\[S = \frac n 2 (a+l)\]

Answer 2

**upto 'n' term^

Answer 3

plug in n=10, a =3, l=75

Answer 4

ok

Answer 5

thats easy, the Formula for sum of the terms is given by S=(n/2)(a+l) where n is the no.of terms, a is the first term and l is the last term.
For your problem the n=10,a=3,l=75

That gives s=(10/2)(3+75)=390

Answer 6

its 390 are you sure thats right?

Answer 7

yes

Answer 8

okay, thanks