Question 1066205
.
Let x be the total population of students in the school.

You are given 0.9x = 1620.


Then x = {{{1620/0.9}}} = 1800.


10% of 1800 is 0.1*1800 = 180.


<U>Answer</U>. 180 students were absent that day.



There is a bunch of lessons on percentage problems 

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/percentage/lessons/Percentage-problems.lesson>Percentage problems</A>

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/Percentage-and-ratio-word-problems/Percentage-word-problems-%28Type-1-problems-Finding-the-Part%29.lesson>Percentage word problems (Type 1 problems, Finding the Part)</A>

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/Percentage-and-ratio-word-problems/Percentage-word-problems-%28Type-2-problems-Finding-the-Rate%29.lesson>Percentage word problems (Type 2 problems, Finding the Rate)</A>

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/Percentage-and-ratio-word-problems/Percentage-word-problems-%28Type-3-problems-Finding-the-Base%29.lesson>Percentage word problems (Type 3 problems, Finding the Base)</A>

in this site.


Read them and become an expert.