The number of people at Ovations Bar in the hour from 12 p.m. to 1 p.m

why in the third passage 7/5??? can explain me ?? please

Sure. The number of people in the bar from 12 - 1:00 pm is 40% greater than the number of people there from 11 a.m. to 12 p.m.
Number of people from 11 am to 12 pm is (3x/4). If we increase (3x/4) by 40%, we get (3x/4) + (40/100)*(3x/4) = (3x/4)(1 + 40/100)
Now, (1 + 40/100) = (1 + 2/5) = 7/5
That is how we get 3x/4 in step 2 too... because no of people from 11 - 12 is 25% less than no of people from 10-11.
x(1 - 25/100) = 3x/4

Generally, it is a good idea to remember fraction equivalents of percentages.
e.g. 50% = 1/2
25% = 1/4
20% = 1/5
etc
So if I reduce x by 25%, I am basically doing the following: x(1 - 1/4) = x*(3/4)
If I increase x by 20%, the I get: x( 1 + 1/5) = x*(6/5)
With some practice, you will be very comfortable with this method and save precious time on the exam.

What if the 11-12 and the 12-1 crowd overlapped? Then you would not know how many were there from 10-11. Seems like a poorly worded question to me. Am I overlooking something?

That is definitely a concern but since it is a problem solving question, we have to work with whatever data we have and arrive at the answer. Hence, it was clear that we do not have to consider that anyone was there in both the slots. In case the question mentioned that 11-12 and 12-1 crowd overlapped, it would have become a sets question. We would have some additional information then e.g. the number of people who were there in both the slots or number of people who were there in only one slot etc. We would have solved it accordingly then.

I do not know how to say thanks......................Thanks a lot

Now it's okkkkk

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