Question

Help!! So confused!

Answer 1

The series in the form of arithmetic progression  
The notation of A.P is a, a+d, a+2d.....
 The summation notation is â‘ 
 In this series a=3, d=7
 Then the summation of A.P is â‘ = n/2(2a+(n-1)d)
  =18/2(2*3+ (18-1)7)
  = 9(6+17(7))
  =9(6+119)
  =9(125)
  = 1125
 Hence the total number of beads is 1125