This Fluency Activity is a part of the Lesson 8, Unit 1, Grade 3. Group counting reviews interpreting multiplication as repeated addition. Counting by twos, threes, and fours in this activity supports work with units of 2 and 3 in this topic and anticipates work using units of 4 in Topic E. T: Let's count by twos to 20. Whisper the numbers, and then speak them. T: Let's count by twos to 20 again. This time, hum the first number, and then speak it.