Problem
For each mountain, add Ms. Reed's count and Mr. Diaz's count: Pine Ridge 5+6=11, Eagle Peak 8+4=12, Mount Rainier 7+9=16, Cedar Butte 3+5=8.
Combining two data tables into one is exactly the picture/bar-graph data sense Grade 3 develops.
3.MD.B.3Organize Information In More WaysAdding a mountain's count in Ms. Reed's table to its count in Mr. Diaz's table gives that mountain's total votes for the two classes together.
On the trip the two classes act as one bigger group, and a mountain's supporters in that big group are exactly its supporters from Ms. Reed's class together with its supporters from Mr. Diaz's class.
Each student belongs to only one of the two classes, so those two sets of supporters never share a student and never miss one — they split the mountain's whole group of supporters cleanly.
When a group is split into parts with no overlap and no gap, counting each part and adding the counts gives the count of the whole group.
The combined votes should equal 23 + 24 = 47. Indeed 11 + 12 + 16 + 8 = 47, so no votes were lost.
Adding the parts to confirm they make the known total is a natural check.
3.OA.D.8Make A Systematic ListThe biggest combined count is 16 for Mount Rainier, more than Eagle Peak's 12, Pine Ridge's 11, and Cedar Butte's 8.
Reading off the largest category from organized data is straightforward graph interpretation.
3.MD.B.3Make A Systematic ListStack the two tables into one and find the tallest count - that's Grade 3 graph reading!