I recently posed a problem on my social networking site: "How do you personally calculate the tip at restaurants?". This question reaped a plethora of responses, each friend sharing their own strategy to find the tip without using a calculator. Among the responses, I would like to highlight three. The first one, which was the most common response, was "doubling the tax". This is a strategy that I use as well, as many of us know that the tax is somewhere between 7.5% and 10%. Simply doubling that number will yield a tip between 15% and 20%, the recommended range for tipping. Another strategy that I found quite interesting was multiplying the total bill by two, and then taking 10% of that by moving the decimal one place to the left. This would yield a 20% tip, but the author also recommended rounding up or down to the nearest dollar depending on the service. Another variation of this was to take 10% of total, and then double that number. Lastly, one friend shared that he tips the total amount divided by 5 in order to yield 20%.
Calculating tip is one of the many ways that everybody uses math in their daily lives, and the variety of ways that people go about this task provides insight into formal, classroom mathematics. Students come into math classrooms with prior knowledge and "street smarts" for arriving at solutions. Sadly, formal mathematics often fails to make connections between students' prior knowledge and the learning goals of the class. Rather, teachers should build on this knowledge, encouraging students to share how they might use their reasoning and logic to find solutions. Lastly, this example also highlights another important goal of teaching mathematics: multiple routes to the same solution. Each "tip strategy" I shared would roughly yield a 20% tip, yet each person had a different way that made sense to them. These multiple routes should be taught and encouraged in secondary math classrooms, providing more opportunities for students to be intellectually creative and to find a way that connects with their own reasoning.
Calculating tip is one of the many ways that everybody uses math in their daily lives, and the variety of ways that people go about this task provides insight into formal, classroom mathematics. Students come into math classrooms with prior knowledge and "street smarts" for arriving at solutions. Sadly, formal mathematics often fails to make connections between students' prior knowledge and the learning goals of the class. Rather, teachers should build on this knowledge, encouraging students to share how they might use their reasoning and logic to find solutions. Lastly, this example also highlights another important goal of teaching mathematics: multiple routes to the same solution. Each "tip strategy" I shared would roughly yield a 20% tip, yet each person had a different way that made sense to them. These multiple routes should be taught and encouraged in secondary math classrooms, providing more opportunities for students to be intellectually creative and to find a way that connects with their own reasoning.
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