What is the sum of the multiples of 4 from 16 to 100?

Answer 1

so you want
16+20+24+...100

number of terms = ??

you have an AS, where
a = 16 , d=4
term(n) = a+(n-1)d
100 = 16 + (n-1)(4)
84 = 4n - 4
88 = 4n
n = 22

so we want S(22)
= (22/2)(first + last) = 11(16+100) = 1276