# Comparing Probabilities of Spinners

The probability of a spinner stopping at a certain area is the ratio of that area to the area of the entire region. Here is a question about comparing probabilities to test your understanding of this concept.

###### Problem

Four students are examining three spinners. They are discussing the probabilities of the spinners stopping at the shaded region.

For each of the following statements, state whether it is **Completely True**, **Partly True** or **Completely False**. If one sentence is true, but the other is false, check **Partly True**.

1. Sherry says, “The probability is twice as large for Spinners 2 and 3 compared to Spinner 1 because they have two regions to stop on and Spinner 1 has only one region.” (**Completely True**, **Partly True** or **Completely False?)**

2. George says, “Spinners 1 and 2 have the same probability since the shaded regions have the same area. Spinner 3, however, has a higher probability than Spinner 2 because the shaded region is a larger area.” (**Completely True**, **Partly True** or **Completely False?)**

3. Paul says, “Spinners 1, 2 and 3 have the same probability because the angles of the shaded regions are the same size.” (**Completely True**, **Partly True** or **Completely False?)**

4. Rainey says, “The probabilities for Spinners 1 and 2 are the same because those areas are the same proportion of the whole circle. For Spinners 2 and 3, however, the probabilities are different because the shaded areas for Spinner 3 are a bigger proportion of the whole square than they are of the circle.” (**Completely True**, **Partly True** or **Completely False?)**

Source of the question: Teacher Education and Development Study in Mathematics (TEDS-M) Policy, Practice, and Readiness to Teach Primary and Secondary Mathematics Conceptual Framework.