Question

Find the partial sum of the first 100 terms of the series 4,8,12,16 .

Answer 1

hello : 
16-12=12-8=8-4=4  ...(common diff by arithmetic sequence)
a1= 4
an = a1+(n-1)r    .. r= 4
a100 = a1 +(100-1)×4 =4+99×4 =  5×99 = 495
the partial sum of the first 100 terms is : S100
S100 = 100/2(4+495) =24950