p_malh wrote:

Hi,

I got 645 too..

the way I solved this problem was to take the combinations where there would be no professors in the group and subtract it from the total no. of combinations-

17C3=680-total comb

7C3=35-no prof at all

680-35=645

Good job. Always look for "complements" to save you lots of time. The GMAT does this a lot.

_________________

Best,

AkamaiBrah

Former Senior Instructor, Manhattan GMAT and VeritasPrep

Vice President, Midtown NYC Investment Bank, Structured Finance IT

MFE, Haas School of Business, UC Berkeley, Class of 2005

MBA, Anderson School of Management, UCLA, Class of 1993