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A supermarket display consists of boxes of cereal. The bottom row has 23 boxes. Each row has three fewer boxes than the row below it. The display has six rows.

AngelRay  May 1, 2018
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Use Arithmetic Series Formulas:

 

a) Nth term = F + (N - 1) x D, where F=First term, N=Number of terms, D=Common difference

6th row = 23 + (6 - 1) x -3

             = 23 + (5) x -3

             = 23 + (-15)

             = 8 - number of boxes in the top row.

 

b) Sum = N/2[2F + (N - 1) x D]

             = 6/2[2*23 + (6 - 1) x -3]

              = 3  [46  +    (5) x -3 ]

              = 3  [46  +      -15 ]

              = 3  [ 31 ]

              = 93 - total number of boxes in the entire display.

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