Problem
Each layer adds 2, so extend 1, 3, 5, 7 to seven layers: the counts are 1, 3, 5, 7, 9, 11, 13 blocks.
Once you see each step adds 2, you can keep counting up by 2 to reach any layer.
4.OA.C.5Look For A PatternThe seven layers use 1, 3, 5, 7, 9, 11, 13 blocks, and each layer holds 2 more blocks than the one before it.
Each L-shaped layer is built from the previous one by setting one extra block on top of its rising side and one extra block on the end of its bottom row.
The taller side and the longer bottom row are separate parts of the figure that share no block, so the new figure's count is the old count plus those two added blocks.
Because that same building step repeats for every layer, each count is the one before it plus 2, so after 1, 3, 5, 7 the counts keep climbing to 9, 11, 13.
Reaching each next layer's count means adding the same fixed amount, 2, onto the running count over and over.
Add the seven counts step by step: 1+3=4, +5=9, +7=16, +9=25, +11=36, +13=49.
Summing a short list of small numbers step by step keeps the running total easy to track.
2.OA.B.2Solve An Easier Related ProblemEach layer grows by 2 blocks, and adding up the odd numbers 1+3+5+7+9+11+13 gives a neat 49!