Question

in an ap, if a=10, d=5 and n=100, then find the value of a100 and also find the 50th term from the end

Answer 1

a100=a+99d
a100=10+99*5
a100=10+495
a100=505
s=ndivided2(2a+(n-1)d)
s=50(20+99*5)
s=50(20+495)
s=50(515)
s=25750