The purpose of this activity is for students to convert between measurements in milliliters and liters, providing practice multiplying and dividing by 1,000. Students work with numbers in many forms, including whole numbers, decimals, fractions, and numbers in exponential form.

• Invite selected students to share how they compared the measurements.
• Display: 15,600 mL and 15.5L
• “How many liters are 15,600 milliliters? How do you know?” (15.6 liters, because I divide by 1,000)
• “How many milliliters are 15.5 liters? How do you know?” (15,500 milliliters, because there are 1,000 milliliters in each liter so that’s 15,000 and half of 1 thousand, which is 500.)
• “Which is greater? 15,600 milliliters or 15.5 liters? How do you know?” (15,600 milliliters, because I can compare them, using either liters or milliliters.)
• “When you solved this problem, did you convert from milliliters to liters or from liters to milliliters? Why?” (I converted from liters to milliliters because multiplying by 1,000 is more comfortable than dividing by 1,000.)

The purpose of this activity is for students to solve multi-step problems involving metric units of liquid volume (MP2). The given quantities involve fractions. One of the quantities involves the fraction , which students may convert to a decimal, or they may perform the needed arithmetic with fractions. Students also have a choice of converting to milliliters or liters, and there are different points in the calculations when they may choose to make the conversion.

Different approaches students may use to solve the problems include:

• Convert the volume of the bottle to liters (as a decimal or a fraction) and work in liters.
• Find out how much each dancer drinks in milliliters, and then convert to liters.
• Find out how much all the dancers drink in milliliters and then convert to liters.
• Find out how much all the dancers drink in milliliters, and then convert the cooler volume to milliliters.

The purpose of the Lesson Synthesis is to compare some of these different approaches.

• Invite a student, who found the number of milliliters all of the dancers drank, to share their reasoning.
• “How did you figure out how many milliliters of water one dancer drinks?” (I took 500 and then half of 500, or 250, more.)
• “How did you figure out how many milliliters all of the dancers drink?” (I multiplied 750 by 25.)
• “How did you find how many coolers the dancers need?” (I multiplied the number of liters in the cooler by 1,000.)
• Invite a student, who found the number of liters all of the dancers drank, to share their reasoning.
• “How are the methods different?” (One method calculates in milliliters and the other method calculates in liters. The numbers with milliliters are much bigger. The numbers with liters are smaller. They are decimals or fractions.)