pikachu wrote:
Fifty percent of all the students attending a school on a certain day arrived by 7:00 AM. How many students arrived by 7:00 AM on that day?
(1) Fifteen students arrived between 7:00 AM and 8:00 AM, and 4/5 of that day’s total attending students arrived by 8:00 AM.
(2) Ten students arrived after 8:00 AM that day.
Can anybody help me understand the question stem. The question is asking how many students arrived by 7:00am on that day but the first part of the question already says 50% of all the students arrived by 7am, so isn't the first part already answering the question itself. Seem confusing.
______________________________________________________________________________
If you like my posts please consider giving kudos
The question asks
How Many? When the GMAT asks "How Many?" it needs a value.
So P = population of the school.
Given: .5P arrived by 7 am
Question is .5P = ?
1.) 15 students arrive between 7 and 8. \(\frac{4P}{5}\) showed up by 8 am.
\(\frac{4P}{5} = .5P + 15\)
You can now solve for P. Sufficient.
2.) 10 students arrived after 8 am.
This tells you nothing about the students arriving between 7 am & 8 am or the total population of the school. Insufficient.
A is the answer.