Question

Help!! So confused!

Dante is making a necklace with 18 rows of tiny beads in which the number of beads per row is given by the series 3 + 10 + 17 + 24 + ...

a. Use summation notation to write the series. Explain what the numbers in the summation notation represent in this situation and how you found the expression used in the summation.

b. Find the total number of beads in the necklace. Explain your method for finding the total number of beads.

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