Gmat Prep: Numbers

take 1: very simple , u know greatest, get the smallest coz nos are consecutive. hence suff.
take 2: find the sum of all the nos by 17.5 * 6 = 105
only one set of consecutive nos adds up to 105 and that is 15,16,17,18,19,20. hence suff.

thus D is the correct answer.

Hi Ketkoag,

How do you know only one set ?(starting with 15) will add up to 105. Is there any formula or something...or have you straightway added the numbers together?

ketkoag wrote:only one set of consecutive nos adds up to 105 and that is 15,16,17,18,19,20. hence suff.

thus D is the correct answer.

there is no as such formula for this, just try to add consecutive nos from any other set and lemme know if u get 105 . the above set is the only set.

Hi ketkoag,
You could put this into a simple formula With the thing we're looking for being 6 consecutive positive integers, you could write a formula such as:

x+(x+1)+(x+2)+(x+3)+(x+4)+(x+5)=105
=> 6x+15=105
=> 6x=105-15
=> 6x=90
=> x=15

This means that 15 is the lowest of the 6, hence the others are 17, 18, 19 and 20.