Question

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 numbers represent an arithmetic progression. The difference between terms is d=7. S=a1+a2+...+an, a1=3 and an=a1+(n-1)×d=3+17×7=122 S=(a1+an)n/2=(3+122)×18/2=125×9=1125