Problem
Using each square = 4 pretzels: 5th = 32, 6th = 16, 7th = 28, 8th = 52, 9th = 36.
Each dot's height times the square value gives that day's count.
3.MD.B.3Draw A DiagramPair to make tens: 32 + 28 = 60, 16 + 36 = 52, then 60 + 52 + 52 = 164.
Pairing numbers to make tens keeps the multi-digit addition simple.
4.NBT.B.4Identify SubproblemsRegrouping the five daily counts into friendly pairs and adding gives the total number of pretzels sold.
The total sold is just the five days' sales combined, so we find it by adding the five daily counts.
The five days are all the days there were, with no day left out and none counted twice, so their counts add back to the whole.
We may reorder the five numbers before adding, because the order we add them in does not change the sum.
We may push different pairs together first, because which two we combine first does not change the sum.
Each pair and the running total are added by combining ones with ones and tens with tens, bundling ten ones into a ten when needed.
Read each day with the right square size, then add - pairing numbers to make tens makes it easy!