Dividing Decimals: Estimation

Explicit Instruction/Teacher modeling

• Write a division problem with decimals on the board (e.g., 11.7 ÷ 4).
• Divide the two whole numbers and explain that since 12 ÷ 4=3, then 11.7 ÷ 4 must be close to 3 (i.e., 11.7 ÷ 4 = 2.94).
• Explain: when we solve the division problem, we are finding the exact answer, or quotient. An estimate is something close to the correct answer, but it is not exact.
• Ask your students, "When might it be helpful to estimate an answer instead of finding an exact answer?" Take student responses.
• Discuss: estimating helps us get close to the answer easily and quickly. Since an estimate is close to the actual quotient, it can also help us check our work. We can estimate an answer to see if our actual answer is close to our estimate. That tells us whether our answer is logical.
• Revisit the problem on the board and ask students to round the decimal to the nearest whole number.
• Divide the two whole numbers and explain that since 12 ÷ 4 = 3, then 11.7 ÷ 4 must be close to 3 (i.e., 11.7 ÷ 4 ≈ 3).
• Compare the estimate to the actual quotient.

Guided Practice

• Write a second problem on the board (e.g., 39.5 ÷ 5). Have students work with a partner to estimate the quotient. Invite a pair of students to show and/or explain their process.
• Write another problem on the board (e.g., 48.3 ÷ 8) and instruct students to estimate the quotient independently. Then, review as a class.

Independent working time

• Hand out the Estimation Station game pieces and have students play the game with a partner.
• Circulate the room as students play and provide support as needed.
• When students are finished, collect the Game Tracking Sheet as one piece of assessment.