Question

A tape diagram. 80 percent out of 100 percent of students had an A or B. 20 students out of question mark students had an A or B. StartFraction part Over whole EndFraction = StartFraction 80 Over 100 EndFraction = StartFraction 20 Over question mark EndFraction
80% of the students in Lea’s class earned an A or a B on the weekly math test. If 20 students got an A or a B, how many students are in Lea’s class?

20 is 80% of what number?
20 × 4 = 80, so 100 × 4 = 400 students
20 + 60 = 80, so 100 + 60 = 160 students
80 ÷ 4 = 20, so 100 ÷ 4 = 25 students
80 – 60 = 20, so 100 – 60 = 40 students

Answer 1

To solve the problem, you want to find out how many students are in Lea's class based on the information that 80% of the students earned an A or B, and that 20 students earned an A or B.

1. You know that 20 students represent 80% of the total number of students (let's call it \( x \)).

The relationship can be set up as:
\[
\frac{20}{x} = \frac{80}{100}
\]

2. To solve for \( x \), you can cross multiply:
\[
20 \times 100 = 80 \times x
\]
\[
2000 = 80x
\]

3. Now, divide both sides by 80 to isolate \( x \):
\[
x = \frac{2000}{80}
\]
\[
x = 25
\]

Thus, the total number of students in Lea's class is 25.

The option "80 ÷ 4 = 20, so 100 ÷ 4 = 25 students" correctly leads to the conclusion that there are 25 students in total in Lea's class.