Doubles Plus One

Overview

Curriculum Area: Mathematics, Grade 2
Specific Domain: Number Sense
California Common Core Standard: CA.Math.2.OA.B.2 - Fluently add and subtract within 20 using mental strategies.

Learning Objective

Students will practice and master the "doubles plus one" addition strategy to improve their mental math skills within 20.

Materials Needed

• Whiteboard and markers
• 23 small whiteboards and markers (one per student)
• Pre-prepared worksheet with 15 doubles plus one problems
• Small erasers
• Stopwatch or timer

Introduction (1 minute)

1. Greeting & Objective: Welcome students and introduce the lesson's focus on the "doubles plus one" strategy. Explain that this strategy helps quickly solve addition problems by using a very close numbers' doubles fact and adding one more.

2. Quick Review: Briefly review how to find doubles (e.g., 4 + 4 = 8). Clarify that "doubles plus one" uses this knowledge to solve something like 4 + 5 as 4 + 4 + 1.

Guided Practice (2 minutes)

1. Demonstration: On the classroom whiteboard, write the problem "6 + 7". Model the doubles plus one strategy:

   • Know that the double of 6 is 12.
   • Add one more to 12 to get 13.

2. Class Participation: Ask students to solve "3 + 4" using their small whiteboards.

   • Double of 3 is 6; plus one makes it 7.
   • Encourage them to write the full process: 3 + 3 + 1 = 7.
   • Walk around the room for quick checks and provide positive affirmations to correct responses.

Independent Practice (2 minutes)

1. Worksheet Activity: Hand out a worksheet with 15 problems specifically designed for "doubles plus one":

   • Example Problems: 5 + 6, 8 + 9, 2 + 3, etc.
   • Encourage students to quickly write down answers using the doubles plus one strategy.

2. Time Check: Use a stopwatch to give students 90 seconds on this task, challenging them to solve as many as they can.

3. Quick Feedback: Once time is up, randomly choose students to share their answers and the doubles strategy they used for various problems.

Conclusion (1 minute)

1. Recap Key Strategy: Reinforce that the "doubles plus one" strategy is about halving the work by jumping from a known double to the target by adding just one.

2. Feedback and Praise: Provide immediate positive feedback for active participation and effort.

3. Closing Statement: Conclude by encouraging students to use this mental strategy in everyday situations for quicker computing.

Differentiation

• Support: Pair students who struggle with a partner or provide them with visual aids such as number lines or counters.

• Challenge: For advanced students, introduce "doubles plus two" to expand their skill set.

Reflection for Teacher

• Observe which students grasp the concept quickly and who may need additional practice.
• Consider incorporating this strategy into daily math warm-ups or games for more reinforcement.

By making this practice session quick and interactive, students will find joy in number play while cementing useful strategies for mental calculations. This approach aligns well with the CA standards for promoting math proficiency at an early age.