A library has an average of 510 visitors on Sundays and 24

[nkmungila1]

A library has an average of 510 visitors on Sundays and 240 on other days. The average number of visitors per day in a month of 30 days beginning with a Sunday is

[A]. 250
. 276
[C]. 280
[D]. 285
[E]. 290

[Jay@ManhattanReview]

A library has an average of 510 visitors on Sundays and 240 on other days. The average number of visitors per day in a month of 30 days beginning with a Sunday is

[A]. 250
. 276
[C]. 280
[D]. 285
[E]. 290

Since the month of 30 days begins on Sunday, the days falling on Sundays would be 1st, 8th, 15th, 22nd, and 29th. Thus, there are 5 Sundays, and 25 other days.

The average number of visitors in the month = [Total number of visitors on Sunday + Total number of visitors on Sunday] / 30

= [Average number of visitors on Sunday * number of Sundays + Average number of visitors on other days * number of days] / 30

= [510*5 + 240*25] / 30 = (5/30)*[510 + 240*5] = (1/6)*[510 + 1200] = 285.

The correct answer: D

Hope this helps!

-Jay

Download free ebook: Manhattan Review GMAT Quantitative Question Bank Guide
_________________
Manhattan Review GMAT Prep

Locations: New York | Barcelona | Manila | Melbourne | and many more...

Schedule your free consultation with an experienced GMAT Prep Advisor! Click here.

[[email protected]]

Hi nkmungila1

Since the average attendance on a Sunday is different from that of any other day, we clearly have to figure out the number of Sundays that we're dealing with (out of the 30 total days). As such, it would likely help to 'draw out' a quick calendar in 7-day increments:

Sun - Sat = 7 days
Sun --> 14 total days
Sun --> 21 total days
Sun --> 28 total days
Sun, Mon --> 30 total days

Thus, we have 5 Sundays and 25 non-Sundays. This is a ratio of 1 to 5, so we can calculate the average attendance using that ratio:

(510 + (5)(240))/6 =
(510 + 1200)/6 =
1710/6 =
285

Final Answer: D

GMAT assassins aren't born, they're made,
Rich

[EconomistGMATTutor]

A library has an average of 510 visitors on Sundays and 240 on other days. The average number of visitors per day in a month of 30 days beginning with a Sunday is

[A]. 250
. 276
[C]. 280
[D]. 285
[E]. 290

Hi nkmungila1,
Let's take a look at your question.

We are asked to find the average number of visitors per day in a month of 30 days beginning with Sunday. Let's find out how many SUNDAYS and how many other days are there in the month.


We can see that there are 5 Sundays and 25 other days in this month.

Number of visitors on 5 Sundays = 5 x 510 = 2,550
Number of Visitors on 25 other days = 25 x 240 = 6,000

Total Number of visitors in the month = 2,550 + 6,000 = 8,550

Average Visitors per day during the month = Total number of visitors / 30
Average Visitors per day during the month = 8,550 / 30 = 285

Therefore, Option D is correct.

I am available if you'd like any followup.

[Scott@TargetTestPrep]

A library has an average of 510 visitors on Sundays and 240 on other days. The average number of visitors per day in a month of 30 days beginning with a Sunday is

[A]. 250
. 276
[C]. 280
[D]. 285
[E]. 290

If a 30-day month begins with a Sunday, then there are 5 Sundays in that month; thus, the average is:

(510 x 5 + 240 x 25)/30 = 8,550/30 = 285

Answer:D