Dividing Decimals By Powers of 10

Explicit Instruction/Teacher modeling

• Review the concept of exponents as powers of ten, connecting them to thoughts that may have been previously shared on the chart paper.
• Demonstrate the procedure for calculating the power of 10 as a whole number equivalent. (For example 10² is (10 x 10), and (10 x 10) is equal to the whole number, 100.
• Note that a whole number like 100, has no exponents and no decimal.
• Using a calculator, model solving 37.5 ÷ 100 for your class.
• Share the answer, or quotient: 0.375.
• Note the movement of the decimal point in the quotient, (0.375) compared to the dividend (37.5)
• Point out that the decimal in the answer has moved two places to the left.
• Ask your students to turn and talk to a partner and describe any patterns they notice in the movement of the decimal and , 37.5 ÷ 10².
• Have your students share out their ideas, whole class and draw make any connections to previous shared information on the chart paper.

Guided Practice

• Show your students the following problem 37.5 ÷ 10⁴ .
• Calculate 10⁴ as a whole number equivalent: 10⁴ is (10 x 10 x 10 x 10), which is equal to 10,000.
• Instruct your class to solve 37.5 ÷ 10,000 with a calculator.
• Tell them to note the movement of the decimal point in their quotient and observe the new position of the decimal from the dividend.
• You should observe that the decimal in the answer has moved four places to the left.
• Explain that today’s lesson requires that your students find the powers of ten as whole numbers, find the quotient to the division problem and describe any recognizable patterns of decimal movement. Calculators will be required. Note any previously shared information on the chart paper that enriches understanding.
• Answer any clarifying questions about the assignment.
• Divide the students into pairs or small groups for independent work time.

Independent working time

• Distribute worksheets and calculators.
• Release your class to work in groups.
• Circulate the room and guide students with leading questions as needed.