Doubles – Doubles plus one - math grade 2 - lesson 11

In math, there are so many ways to solve addition and subtraction problems. We are going to work on ways to solve these problems using MENTAL MATH STRATEGIES over the next few days. This means we will think about the numbers in our minds in lots of ways to find the answers. The first MENTAL MATH STRATEGY we are going to practice is called Doubles. You may remember this strategy from last year, but let’s do a quick review. Doubles is when you think about adding two numbers that are the same. Let me show you what I mean.

TEACHER DO: Hold up 3 fingers on one hand and 3 fingers on the other hand.

TEACHER SAY: What do we get if we put 3 and 3 together?

STUDENTS DO: Raise hands to volunteer. Selected students share their answers.

2.TEACHER SAY: Yes, 3 plus 3 is 6. You will practice this with a partner now. Please turn to your Shoulder Partner and put one hand behind your back. With the other hand, each of you show 4 fingers.

STUDENTS DO: Turn to their Shoulder Partner, put one hand behind their back, and hold out 4 fingers on the other hand. Together, partners figure out the sum of 4 and 4.

TEACHER SAY: So what do we get when we add 4 and 4? Call out together.

3.TEACHER SAY: Yes, 4 plus 4 is 8. You will now work with your Shoulder Partner to practice finding doubles. Open your student book to the page Lesson 11: Apply. Complete only the table at the top of the page.

STUDENTS DO: Turn to Lesson 11: Apply in the student book and work with partner to complete the doubles table.

TEACHER DO: When students are finished, call a pair of Shoulder Partners to the board to fill in the class Doubles Chart. Encourage students to change their answers if they got the incorrect answer.

STUDENTS DO: Selected students show their work at the board.

4.TEACHER SAY: Now we will Apply the Doubles strategy to help us do some mental math. Since we know 3 + 3 equals 6, we can use this double to help us solve 3 + 4. 3 plus 4 is the same as double 3 plus 1 more. Who can tell us the answer?

STUDENTS DO: Selected students answer.

TEACHER SAY: Yes, the answer is 7. Let’s try another one together. What double can help us solve 6 + 7?

TEACHER DO: Call on a student using the Calling Sticks. Listen for the answer, 6 + 6. Ask students to explain their thinking. Listen for “6 + 7 is close to 6 + 6, so since I know the doubles of 6, I can do double 6 plus 1 more.” Some students may also identify 7 + 7 as a helpful double since 6 + 7 is 1 less than 14.

5.TEACHER SAY: Using the mental math strategy Doubles can help us quickly solve math problems in our heads without using our fingers or counters. Now you will work on your own. Use the Doubles mental math strategy to solve the addition problems in your student book.

STUDENTS DO: Work independently to solve the addition problems by applying the Doubles mental math strategy in their student books.

TEACHER DO: Walk around the room to assist students as needed. Take note of students who may need additional instruction.