Posted by sam on .
A speaker was so boring that onehalf of the audience left after a few minutes. Five minutes later, onethird of the remaining audience left. Ten minutes later, onefourth of those remaining left, leaving only nine people in the audience. How many people were in the audience at the beginning of the lecture.

Math 
helper,
x = people in audience
1/2 x = left 1st
1/3 (1/2 x) = 1/6 x = left next
1/4 (1/3)(1/2)x = 1/24 x = left last
x  (1/2 x + 1/6 x + 1/24 x) = 9
Solve for x