Dividing Decimals by Whole Numbers
Lesson 23 of 26
Objective: SWBAT divide decimals by whole numbers using the standard algorithm.
Students will be completing whole number division problems. I want the students to re-engage with division, knowing what number is placed in the division house and what number becomes our divisor. Students should be able to set up and solve these division problems independently. If students have difficulty figuring out where to put the numbers, have them read it out loud. This should help them figure out that the second number belongs as our divisor. (SMP 1 ,2 ,6)
To go over these problems, have the students explain the steps to get to their solution. This will help develop the understanding of how to divide decimals by whole numbers.
Students should take notes on how I model dividing decimals by whole numbers. I’m going to have the students estimate an answer to help with decimal placement. Students should see that dividing decimals is similar to dividing whole numbers. The placement of the decimal rises into the quotient. Do several problems with the students before letting them work independently.
Allow the student time to work independently on dividing decimals by whole numbers. Estimation will assist with the placement of the decimal. As students work through each problem, have them keep track of a step by step way to solving the problem. We will discuss this after the students have had time to develop their thinking. During this portion, you could have the students write their solutions on a white board to do a formal assessment of who is getting it and who is not. Students can work the problem out on their paper; write the solution on a white board. When the majority of the group has completed the problem, call for a white boards up and check their solutions. Call on random students to explain how they got their answer.
When you feel the students understand how to solve the problems, have the students explain the steps to finding the answer to a decimal division problem. These steps can be written in their notes.
The students will be using real world problems involving division of decimals. Students should always correct the work of the person who passed their paper to them before moving to a new problem. Correction of work can be re-working the problem or multiplying the quotient by the divisor to see if they get the dividend. (SMP 1,2,3,6)
Two problems to keep an eye out for are:
Problem 2: The students will need to use zero as a place holder. This is a common problem with division.
Problem 3: This problem can be solved in 2 ways. The unit rate for one of the comparisions is already given. They can compare the other product by using the unit rate. Or they can take the product that is already expressed in the unit rate and mulitply it by 6 to compare equal parts. Either way is an acceptable way to solve.
The roundtable structure is a great way to implement MP 3 because students are checking each other's work by multiplying or re-doing the problem which is an example of critiquing each other's work.
To bring this lesson to an end, I will be going over the problems from the round table. There are 4 problems to be discussed. Ask students to come to the board to show how they solved the problem. As students are walking through the process, ask the students watching “why” they did it. It’s important that all students are involved in this process. Knowing that they may be called on to answer the why will help increase the level of concern and maintain focus. (SMP 1,2,3)