Problem
Subtract the three known categories from the total to get the number of students who like roses.
A total is the sum of its parts, so the missing part is the total minus the known parts.
3.MD.B.3Identify SubproblemsThe number of students who like roses is the total of 64 minus the three known counts, which comes to 22.
The four flower counts are the parts that make up the whole group of 64 students, so the four counts together must equal 64.
Each student picks exactly one favorite flower, so the four groups cover everyone once with no overlap and add back to the whole total.
When the whole and every part but one are known, taking the known parts out of the whole leaves the one part that is still missing.
Removing the known counts from the total undoes the addition that first combined the parts, so subtraction gives back the rose count.
Compare the four counts: 22 (rose), 18 (tulip), 10 (lily), 14 (daisy). The largest is 22, so the scale must reach at least 22 students.
The tallest bar sets how high the scale must go.
3.MD.B.3Identify SubproblemsEach grid square is worth 2 students, so divide the largest value by 2 to find how many squares are needed.
If one square holds 2 students, then 22 students fill 11 squares exactly.
3.MD.B.3Analyze The UnitsThis only needs Grade 3 bar-graph sense: find the biggest value, then count squares worth 2 each!