Joe Komagawa
Average Member
Japan
11 Posts 
Posted  12/01/2013 : 01:10:56

GMATthe official guide, #174 (box triangle)(triangle)(box)= box, triangle box the product of 2 digit numbers above is the 3 digit number "boxdiamondbox" where box, diamond, triangle are nonzero digits. If (box)(triangle) <10, what is the 2 digit number boxtriangle? A) 11, B) 12, C) 13, D)21, E) 31 Answer: D) 21 OK, the key in the answer is to know that triangle= 1, and I don't see ( and 2 smarter friends don't see how this conclusion is brought about.
Where does "(box)(triangle) = box " come from in this deductive process? and the rest of the explanation, "Notice that the hundreds digit in the solution is the same as the hundreds digit of the second partial product, so there is no carrying over from the 10s column. this means that "diamond<10 and since diamond=(box)(box)+1".... Help!
THANKS FOLKS! , I spent about 2 months of squeezing my tiny brain over these 176 problems. There is 1 more but I didn't include it here. I think I am testing your patience. BUT, really I have really really tried to work alll these by myself,and in addition I have gone back over the problems I muddled through, in some cases several times. to try to get the thinking of the mathematical way. Regards from Starbucks in Saitama Japan, Joe 

