Question

The answer to this question 180, but how?

One day 10% of the students enrolled in the school were absent, There were 1620 student present on that day. How may students were absent.

I know you have to figure what percent of the students were present.

Answer 1

I'm going to show you two ways to do it.
Way #1 is the slogging way.
Way #2 is the clever way.


Way #1:

' One hundred percent ' means ALL of something.
ALL of the students in the school is the same as 100% of them.
If 10% are absent, then 90% are present.
90% means 0.9 .

1620 students = 90% of the school.

1620 = 0.9 x school total

Divide each side by 0.9: 1620/0.9 = total school

1800 = total school

How many were absent ?
10% of them.
10% means 0.10 .

0.10 x 1800 = 180 students absent .
_______________________________________

Way #2:

' One hundred percent ' means ALL of something.
ALL of the students in the school is the same as 100% of them.

==> If 10% are absent, then 90% are present.

==> The number of students present is 9 times the number who are absent.

1620 = 9 x the number absent

Divide each side by 9 : 1620 / 9 = the number absent

1620 / 9 = 180 absent .