the first term of an arthmetic progression is 1 and its last term is 28, find the sum of the progression if their number is 10
a=1
n=10
a+ 9d = 28
9d = 27
d = 3
sum(10) = 10/2(first + last) = 5(1+28) = 145
n=10
a+ 9d = 28
9d = 27
d = 3
sum(10) = 10/2(first + last) = 5(1+28) = 145