Huh. Interesting topic! When I lived in an area where tax was ~7-8%, people used the heuristic of "doubling the tax" and adjusting from there. I calculate 10%, double it, and go from there. As an aside, my experience over the past ~5 years is that 15% is a minimum and closer to 20% is more typical. Is that just the 25-35 set I spend time with?
Patrick ********************** Patrick O. Dolan Assistant Professor Department of Psychology Drew University Madison, NJ 07940 973-408-3558 [EMAIL PROTECTED] ********************** ----- Original Message ----- From: "Paul Smith" <[EMAIL PROTECTED]> To: "Teaching in the Psychological Sciences" <[EMAIL PROTECTED]> Sent: Friday, August 08, 2003 10:39 AM Subject: Tips on Tipping > As I think the original request was for common behaviors that can be related > to psychological topics, I think the question of how one figures a standard > tip is also interesting. I see people using little "tip tables" that give > 15% of various amounts in table form, but without such a table, how one > represents the problem can make a big difference in problem difficulty. > We're taught to figure things like this by multiplying the total bill by > .15, and we're taught to do problems like that using a complicated > algorithm* that amounts to manipulation of symbols. That algorithm is too > complicated for most of us to do mentally, without at least writing down > intermediate answers, something which is often not possible when figuring a > tip (due to lack of pencil and paper). > > But there are other ways to figure 15% besides that kind of symbol > manipulation. I usually figure 10% (simply by moving over the decimal point > mentally), and then figure (again, mentally) half of that number (which is > then 5% of the total), and then (yet again mentally) add the two. > Alternatively, one could figure 10%, and then 20% (simply by doubling the > 10%) and then figure the halfway mark between those two numbers (I haven't > used that method, and I don't know if it would be too taxing for me). > > I'll bet there are other ways that people use besides these, and I'd think > they might lead to an interesting discussion of the role of mental > representation in mathematical problem solving. Most Introductory texts have > a chapter on "Language, Thinking, and Problem Solving" where the relevant > material would be found. I suspect that most of the people who still try to > use the symbol manipulation algorithm in the tipping context also believe > that symbol manipulation method they've been taught IS multiplication, and > don't realize that it's just one of many devices for finding the answer to > multiplication problems. > > * "Okay, class, remember, start by multiplying the ones column, and write > your answer below the ones column, carrying any tens you get up to the top > of the tens column. Then take the tens column from the first multiplicand > times the ones column from the second..." > > Paul Smith > Alverno College > Milwaukee > > > --- > You are currently subscribed to tips as: [EMAIL PROTECTED] > To unsubscribe send a blank email to [EMAIL PROTECTED] > > --- You are currently subscribed to tips as: [EMAIL PROTECTED] To unsubscribe send a blank email to [EMAIL PROTECTED]
