Question

the first term of an arithmetic sequence is 10 and the twentieth term is 60.calculate the sum of first 20 terms​

Answer 1

Answer:

a=10

twentyth term is =10+ 19(d) =60

=19d=50

d=50/19

sum of 20 terms=20/2(20+19(50/19)

=10(20+50) =10(70) =700