Think of the fraction from the sample as representing the proportion of all students at the school. How can you write an equation that compares the sample fraction to $x/500$ for the whole school?

You can either solve $6/25 = x/500$ by cross-multiplying, or multiply the sample proportion by 500. Remember that $500/25$ is a simple number.

Once you find the estimated number of students, look at the choices and select the one that equals your result.

In Desmos, type the expression (6/25)*500. The output shows the estimated number of students in the entire school who drink at least 8 glasses of water per day; choose the answer option that matches this value.

From the sample, 6 out of 25 students drink at least 8 glasses of water each day.

Write this as a fraction: $6/25$.

Now convert $6/25$ to a decimal or percent:

• $6 \div 25 = 0.24$, which is $24\%$.

Assume the same proportion holds for the entire school of 500 students.

Set up a proportion:

where $x$ is the estimated number of students in the whole school who drink at least 8 glasses of water each day.

Solve the proportion for $x$.

You can multiply the fraction by 500:

First compute $500 \div 25 = 20$, then:

So the best estimate is $120$, which corresponds to choice D.