GRE Math Problem 51

Two researchers spent a total of 35 hours on a certain project. One of the researchers spent 25 percent fewer hours on the project than the other.

Column A	Column B
The difference between the number of house spent by each	7

Solution for GRE Math Problem 50:

The sandwich with, let's say, lattuce on onion and the the sandwich with onion on lattuce are different sanwiches. So, to calculate the total number of sandwiches, we should use arrangements, not combinations. number of arrangement of m items out of n ones is A(n,m)=n!/(m-n)!=n*(n-1)*(n-2)*...*(n-m+1) A(4,1)=4 A(4,2)=4*3=12 A(4,3)=4*3*2=24 A(4,4)=4*3*2*1=24 Total 24+24+12+4=64>32. Answer:A

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