25% of the students in a class got an A+ on a test. 30% of the rest got an A−. 40% of the rest got grade B. The rest of students scored lower than B. What percent of all students got a grade lower than B?
5% of the students got a grade lower than B. The percentage of students in each category should sum up to 1, or 100% of the students. Therefore, 100%-25%-30%-40%=5% of the students scored lower than B.
