SOLUTION: A speaker was so boring that one-half of the audience left after a few minutes. Five minutes later, one-third of the remaining audience left. Ten minutes later, one-fourth of thos

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Question 290453: A speaker was so boring that one-half of the audience left after
a few minutes. Five minutes later, one-third of the remaining audience left. Ten minutes later, one-fourth of those remaining left, leaving only nine people in the audience. How many people were in the audience at the beginning of the lecture?
(a) 21 (b) 36 (c) 72 (d) 144 (e) 216

Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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one-half of the audience left after a few minutes.
Five minutes later, one-third of the remaining audience left.
Ten minutes later, one-fourth of those remaining left, leaving only nine people in the audience.
How many people were in the audience
:
Let x = no. in the audience
:
"one-third of the remaining audience left.
that leaves 2/3
2%2F3*(1%2F2x) = 2%2F6x = 1%2F3x
:
"one-fourth of those remaining left,"
that leave 3/4
3%2F4*1%2F3x = 3%2F12x = 1%2F4x
:
"leaving only nine people in the audience. "
1%2F4x = 9
Multiply by 4
x = 36 people in the audience