Answer
See below
Work Step by Step
The number of blocks in the nth layer is $a_n=n(n+1)$
Since there are 4 layers, the sum then will be $\sum^4_{i=1}a_i=\sum^4_{i=1}i(i+1)$
Hence, the correct answer is D.
Algebra 2 (1st Edition)
by Larson, Ron; Boswell, Laurie; Kanold, Timothy D.; Stiff, Lee
Published by
McDougal Littell
ISBN 10:
0618595414
ISBN 13:
978-0-61859-541-9
Chapter 12 Sequences and Series - Standardized Test Practice - Multiple Choice - Page 846: 7
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