IMO, for such small ranges it is quicker to just enumerate the numbers and list the prime numbers. At a general level, in a set of any ten consecutive numbers (like 11-20, 32-40, 151-160 etc) there will be 2 number divisible by 5, 4 number divisible by 2 (taking the one's ending with 0 under divisib...

GMATPrep Q on SC

Radiocarbon dating of fossils taken from caves on islands along southeastern Alaska's coast suggest that at least a portion of the area was remaining ice-free during the last ice age. a. suggest that at least a portion of the area was remaining b. suggest at least a portion of the area remaining c. ...

DS question on Sum of consecutive postive integers

The sum of n consecutive positive integers is 45. What is the value of n?

(1) n is even

(2) n < 9

OA is E. What will be the quickest way to solve this?

Starxxx, I feel that these type of problems eat away extra time on the GMAT. Not sure how to tackle them, other than take a smart guess and move on. Cracking such questions in one shot in less than 3 minutes is highly doubtful.

Let R be the radius of bigger circle and r be the radius of the smaller one.
Then
*Note Pi is denoted by #
((#R^2)-(#r^2)/(#r^2))=3/1
=> #R^2=4#r^2
=> R=2r

Ratio of Circumference of the two circles is the ratio of the radius
Hence R/r=2 from above.
Correct answer is 2.

OA is E. Thanks for the explanation.

I am not sure as to what exactly is the inequality, since formatting is messing up what you've written.

Question involving absolute values

If a and b are integers, and |a| > |b|, is a · |b| < a – b?

1. a less than zero
2. ab greater than equal to zero

Would love to see explanation for this one. Can this be cracked in 2 min time?