Question

Last time, one out of every 4 students in our class was absent. This time, after Jen came back, only one out of every 5 students is absent. How many students are there in our class? How many students are not here today?

Answer 1

Answer: There are 20 students and 4 students are not here today.

Step-by-step explanation:

If the number of students = 4

Let the number of students be 'x'.

Fraction of students absent = $\dfrac{x}{4}$

If the number of students = 5

Fraction of students absent = $\dfrac{x}{5}$

And Jen came back,

So, the fraction of student absent is also written as

$\dfrac{x}{4}-1$

According to question, it becomes,

$\dfrac{x}{5}=\dfrac{x}{4}-1\\\\\dfrac{x}{5}=\dfrac{x-4}{4}\\\\4x=5(x-4)\\\\4x=5x-20\\\\4x-5x=-20\\\\-x=-20\\\\x=20$

Hence, there are 20 students in our school.

And number of students are not here today is $\dfrac{20}{5}=4$