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Should fast food restaurants rewrite their menus in terms of exercise? According to the McDonald’s menu, a Big Mac contains 540 calories. But what does that really mean...and would it be more helpful to describe this as “65 minutes of running”?

In this lesson, students write and evaluate expressions to determine how long it takes to burn off foods from McDonald’s and debate the pros and cons of including this information on fast food menus.

REAL WORLD TAKEAWAYS

How many calories we burn depends on our weight, the activity we’re engaged in (some burn more than others), and how long we engage in that activity.

We can calculate how many calories we need for a specific activity; we can also calculate how long we’d need to engage in a certain activity to burn off some number of calories.

MATH OBJECTIVES

Use rate and ratio reasoning to solve real-world problems

(Optional) Write and solve one-step equations to determine how much exercise would be needed to burn off different food items.

Great anytime, including at the beginning of a unit before students have any formal introduction to the topic.

Grade 6

Equations & Expressions

Grade 6

Equations & Expressions

Content Standards
6.RP.3
Use ratio and rate reasoning to solve real-world and mathematical problems, e.g., by reasoning about tables of equivalent ratios, tape diagrams, double number line diagrams, or equations. (a) Make tables of equivalent ratios relating quantities with whole- number measurements, find missing values in the tables, and plot the pairs of values on the coordinate plane. Use tables to compare ratios. (b) Solve unit rate problems including those involving unit pricing and constant speed. For example, if it took 7 hours to mow 4 lawns, then at that rate, how many lawns could be mowed in 35 hours? At what rate were lawns being mowed? (c) Find a percent of a quantity as a rate per 100 (e.g., 30% of a quantity means 30/100 times the quantity); solve problems involving finding the whole, given a part and the percent. (d) Use ratio reasoning to convert measurement units; manipulate and transform units appropriately when multiplying or dividing quantities.
6.NS.3
Fluently add, subtract, multiply, and divide multi-digit decimals using the standard algorithm for each operation.
6.EE.2
Write, read, and evaluate expressions in which letters stand for numbers. (a) Write expressions that record operations with numbers and with letters standing for numbers. For example, express the calculation "Subtract y from 5" as 5 — y. (b) Identify parts of an expression using mathematical terms (sum, term, product, factor, quotient, coefficient); view one or more parts of an expression as a single entity. For example, describe the expression 2 (8 + 7) as a product of two factors; view (8 + 7) as both a single entity and a sum of two terms. (c) Evaluate expressions at specific values of their variables. Include expressions that arise from formulas used in real-world problems. Perform arithmetic operations, including those involving whole-number exponents, in the conventional order when there are no parentheses to specify a particular order (Order of Operations). For example, us the formulas V = s<sup>3</sup> and A = 6s<sup>2</sup> to find the volume and surface area of a cube with sides of length s = 1/2.
6.EE.6
Use variables to represent numbers and write expressions when solving a real-world or mathematical problem; understand that a variable can represent an unknown number, or, depending on the purpose at hand, any number in a specified set.
6.EE.7
Solve real-world and mathematical problems by writing and solving equations of the form x + p = q and px = q for cases in which p, q and x are all nonnegative rational numbers.

Mathematical Practices
MP.3
Construct viable arguments and critique the reasoning of others.
MP.1
Make sense of problems and persevere in solving them.
MP.2
Reason abstractly and quantitatively.
MP.7
Look for and make use of structure.