Problem 473

Denise is designing the seating arrangement for a concert an outdoor theater. To give everyone a good view, each row must have 6 more seats than the row before it, and the first row can only have 11 seats. Help Denise plan the rest of the seating by solving for how many seats are in row 18. Then explain to Denise how to create an equation to predict the number of seats in any row. Show your work, and use complete sentences.


number of seats in first row are 11 seats,
there are increment of 6 seats in every next row, so this is arithmetic series,
so we can use the formula of arithmetic series’s nth term :
a(n) = a(1) +(n-1)d
seats in 18th row, so given values are a(1) = 11, n=18, and d=6
a(18) = 11+(18-1)(6)
a(18) = 11+17*6
a(18) = 11+102
a(18) = 113
So there are 113 seats in 18th row.


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