Multiply Decimals and Whole Numbers

10 min

Narrative

The purpose of this True or False is to consider relationships between place values. This recalls work that students did earlier in the unit. Seeing these relationships expressed using multiplication naturally prepares students for the work of the next several lessons where they will learn to find products of decimals. Students will revisit multiplicative relationships of place values in a later unit.

Launch

  • Display one statement.
  • “Give me a signal when you know whether the statement is true and can explain how you know.”
  • 1 minute: quiet think time
Teacher Instructions
  • Share and record answers and strategy.
  • Repeat with each statement.

Student Task

Decide if each statement is true or false. Be prepared to explain your reasoning.

  • 100×0.01=1100 \times 0.01 = 1
  • 10×0.1=0.0110 \times 0.1 = 0.01
  • 10×0.01=0.110 \times 0.01 = 0.1

Sample Response

  • True: There are 100 hundredths in a whole.
  • False: There are 10 hundredths in a tenth not ten tenths in a hundredth.
  • True: There are ten hundredths in a tenth.
Activity Synthesis (Teacher Notes)
  • Display: 100×0.1100 \times 0.1, 10×0.110 \times 0.1, 10×0.0110 \times 0.01
  • “What is the same and different about these expressions?” (They all have multiples of 10 in them. They all have decimals. The values are all different.)
Standards
Building Toward
  • 5.NBT.7·Add, subtract, multiply, and divide decimals to hundredths, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used.
  • 5.NBT.B.7·Add, subtract, multiply, and divide decimals to hundredths, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used.

15 min

20 min