SOLUTION: If 3/4 of a class is absent and 2/3 of those present leave the room. What fraction of the original class remains in the room?

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Question 295603: If 3/4 of a class is absent and 2/3 of those present leave the room. What fraction of the original class remains in the room?
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
"If 3/4 of a class is absent", then 1-3%2F4=4%2F4-3%2F4=%284-3%29%2F4=1%2F4 of the class is present. Now since "2/3 of those present leave the room", this means that 1/3 of those present remain in the room. So simply multiply 1%2F4 by 1%2F3 to get the number of the people who remain the room. So %281%2F4%29%281%2F3%29=%281%2A1%29%2F%284%2A3%29=1%2F12



So 1%2F12 of the original class remains in the room.

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Here's a concrete example: Say there are 600 kids. Now if "If 3/4 of a class is absent", then 600%283%2F4%29=450 kids are absent and 600-450=150 are present (in the beginning)

Now because "2/3 of those present leave the room", we know that 150%282%2F3%29=100 kids leave the room. Because 150 kids showed up originally, this means that 150-100=50 kids remain. Now just compute the ratio of the remaining 50 students to the total of 600 to get 50%2F600=1%2F12 which is the fraction we originally found. So this example supports our answer.