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