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
