Problem
Adding every town's circles gives 2+2+4+1=9 in all.
The 18 students are exactly the ones the circles show, with none left out and none counted twice. So adding up each town's circles gives the total circle count — the number we'll use to split 18 in the next step.
Identify Subproblems3.MD.B.3Tables And Graphs9 circles equal 18 students, so one circle is worth 18÷9=2 students.
Nine equal circles building up to 18 students is a multiplication (9 × one circle = 18). Division reverses multiplication, so if 9 times one circle equals 18, one circle equals 18 ÷ 9.
Analyze The Units3.MD.B.3Each circle in the graph stands for 2 students.
The 9 circles together stand for all 18 students and every circle is worth the same amount, so one circle's value is 18 split evenly into 9 equal parts.
The 18 students are exactly the students shown by the circles, with none left out and none counted twice, so the circle amounts add back up to 18.
Nine equal circles building up to 18 students is a multiplication, so the size of one circle is found by reversing it with division.
Nine circles each worth the same is nine equal groups, and counting equal groups is exactly what multiplication does, so 9 times one circle's value is 18.
Division is the reverse of multiplication, so from 9 times one circle equals 18 we get that one circle equals 18 divided by 9.
Town C has 4 circles, so its students are 2×4=8.
Once one circle is known to be a group of 2 students, Town C's 4 circles are 4 equal groups of 2. Counting equal groups with multiplication, 2 × 4, gives Town C's real number of students.
Analyze The Units3.MD.B.3When a picture graph has no scale, match the total circles to the total value to find one circle's worth first.