Question

John's class has 30 students, 22 of the students have brown hair. If there are 180 students in the school, how many students could you predict to have brown hair?

Answer 1

Equivalences

Initial explanation

We have that if we have 30 students, 22 of them will have brown hair. This can be expressed as the relation:

30 students ⇔ 22 students with brown hair

If there are 180 students, we have a certain number of students with brown hair

180 students ⇔ ??

Writing the equivalence

Then, we have the following equivalence

180 students ⇔ ??

30 students ⇔ 22 students with brown hair

Writing an equation

If we divide each side of the equivalence we will have the same result:

$\frac{180}{30}=\frac{?\text{?}}{22}$

We want to find the number ??, then we take 22 to the left side of the equation:

$\begin{gathered} \frac{180}{30}=\frac{?\text{?}}{22} \\ \downarrow \\ \frac{180}{30}\cdot22=?\text{?} \\ \downarrow \\ 132=?\text{?} \end{gathered}$

Then, we can predict that there will be 132 students with brown hair.

Answer: 132