Incomplete question. However, let's assume the number of students in Charles's lab group is 7. In the diagram, a circle represents a student, and a rectangle represents a test tube.
Step-by-step explanation:
Then, numerically 4 (test tube) x 7 (students) = 28, However, by making a comparison between two quantities we can observe from the attached image that there are indeed 4 times as many test tubes (rectangles) as students (circles).