Engaging Math Activities for Students - Double and Half Strategy Explained

Teachers Notes Teacher s Notes Accept any reasonable answers on the second student slide. a) Perimeter = 14 b) Perimeter = 16 c) Perimeter = 26 Double Half Double Half

Teachers Notes Teacher s Notes Answers: For the white board questions ( there are 10 stop sooner if students tire) , use a game format if possible. But make sure the game doesn t draw attention to incorrect answers. For example: Two points every time I see x correct answers, and one point if I see y correct answers. . Points count towards a reward. Choose the number x as three less than the number of students in your class, and y at 5 less, so that an occasional mistake doesn t hurt the group effort. Of course, we fudge about the number of correct answers we see, too, to help students save face. Be careful to GIVE ENOUGH TIME. Those students who write the answer and hold it up can wait the 5 seconds while others are still thinking and writing. You might say Show me your board, and then take it down, and write down the name you would choose if you got a new pet. Or what you would buy if you earned $10 mowing the lawn , etc. It s so important for the students who need more time to NOT get frustrated because they need those extra few seconds. 1. 10x8 = 80 2. 8x11 = 88 3. 8x8 = 64 4. 10x9 = 90 5. 8x6 = 48 6. 10x24 = 240 7. 4x70 = 280 8. 30x9 = 270 9. 90x6 = 540 10. 2x600 = 1200

What is Double and Half ?? 2

Youll need 12 blocks. You ll need 12 blocks. a) Lay out a rectangle of 3 x 4 blocks. What is the perimeter? b) Can you build a rectangle with the same number of blocks, but with a perimeter of 16? c) Can you build a rectangle with the same number of blocks, but with a perimeter of 26? Write out the 3 multiplication problems. How could these 3 problems illustrate the DOUBLE AND HALF strategy? DOES IT ALWAYS WORK??? 3

Six dots, in 8 rows. Twelve dots, in 4 rows. Double and Half

You try it! Youll need a white You try it! You ll need a white board and marker. board and marker. 6

1

8 16 5 10

2

11 22 4 8

Half and Double works too!! 3

8 16 4 8

4

Half and Double works too!! 5

6

= 4 70 = 4 7 10 7 Hundreds Tens 2 Ones 8 0

= 30 9 = 3 9 10 Hundreds Tens 2 Ones 7 0 8

= 90 6 Hundreds Tens 5 Ones 4 0 9

16 75 = 8 150 = 4 300 10 10