Joined: 09 Mar 2003
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1. Realize that if there were 12 more shares and 15 more dollars, the shares are worth more than a dollar a share, so there would have to be less than 160. Cancel out c, d, e.
2. Now there are at least three ways of doing it, all of which depend on who you are and how you think. I'll put as many below as I can think of - I think they're all fine and expediant. Remember - if you're spending time looking for the most sophisticated way, you could be just wasting time, especially if you know how to do it algebraically.
Method 1: Algebra
160/x = 175/(x+12)
That's because each stock is worth the same, so if you divide the 160 by the number of shares, or 175 by the number of shares plus 12, you get the same answer. Solve for x = 128.
Method 2: 12 more shares cost $15, so that means each one cost $1.25. So 160/1.25. To do this quickly, convert 1.25 into 5/4 (I LOVE FRACTIONS!) Now you've got 160/(5/4) = 160x4/5 = 32x4 = 128.
Method 3: Once you've cancelled c,d,e, you can plug in a or b and see what happens. One will work and one won't, but either way, after just one time through, you'll have your answer.