Ten percent of the class period was spent taking roll and making announcements. If there were 45 minutes that remained, how long is the class period?
Show answer but also explain it plz so I understand it
+9481 Let's call the length of the class period " p ".
From the problem statement, we can make this equation:
p - 10% of p = 45 minutes
p - 0.1p = 45 minutes
0.9p = 45 minutes (In other words, 90% of the class period is 45 minutes.)
Divide both sides of the equation by 0.9 .
p = 45 / 0.9 minutes
p = 50 minutes 
+9481 Let's call the length of the class period " p ".
From the problem statement, we can make this equation:
p - 10% of p = 45 minutes
p - 0.1p = 45 minutes
0.9p = 45 minutes (In other words, 90% of the class period is 45 minutes.)
Divide both sides of the equation by 0.9 .
p = 45 / 0.9 minutes
p = 50 minutes
