I realized recently that my students have forgotten how to round since the beginning of the school year. Yay! Something else I get to go back and reteach!
I found a book called, Memory Tips for Math, by Donnalyn Yates. There is a plethora of information in here to help teach students to remember math concepts taught in class.
One idea to help students remember how to round is to draw the following picture:
A waved line resembling mountains on the board or a long piece of paper. Put 0, 10, 20, 30, etc in the valley depressions and 5, 15, 25, etc at the top of each peak. Write the numbers 1-4 up the left side of the mountain and 6-9 on the right. Use a magnet or interactive white board picture to simulate going on a trip over the mountain. Pick a number between 1-9. If the nubmer ends in 1-4, drive the car to that number, get out to look at the view and forget to put on the brake. Ask students what will happen to the car? Discuss whether it will roll up the hill to the next number or back down to the lower number. Talk about the fact that a car won't roll up a hill.
If the number ends in 6-9, repeat the process with the car and continue the discussion. This is so useful with your visual learners!
I used the Rounding Round Up song/chant to help me students remember when to round.
Another useful method for students who respond well to procedural methods is as follows:
What is 27 rounded to the nearest 10?
Underline the place value you need to round to. Circle the number to the right and ask is it larger or smaller than 5? If it's larger, round up the underlined number up one. If smaller, it stays the same and you replace the number in the ones with a 0.
You can use this method with the Rounding Round Up chant or the Rounding the Mountain picture.
Other chants and memory tricks I've seen:
1. 1 through 4, stay on the floor. 5-9 climb the vine!
2. Four or less, give it a rest. Five or above, give it a shove.
3. You tell a story about a criminal (the number to be rounded), a judge (the number that determines the rounding) andthe jury (the rest of the numbers. In order to find out whether or not the crimimal has to stay in jail he must go to the judge and ask. If the judge is a strict one (a number of 5-9)then he must stay in jail one more year. He goes up one number. Then the judge and the jury go to lunch and are replaced by zeros. If the judge is a weak one (number from 0-4) he or she says ahhh you can go and i won't make you change. Then he goes to lunch with the jury and the numbers are replaced with zeros. So in the number 457 - where 4 is the criminal, 5 is the judge and 7 is the jury. 5 is a strict judge and makes the 4 stay in jail one more year. The 4 becomes a 5 (because the judge is strict and makes hime change). Then the judge goes to lunch with the jury (the 7) and they are replaced by zeros. The number becomes 500.
4. Rounding Rap
Find that place value, circle that digit.
Number to the right, underline, get it.
Four and under, circle stays the same.
Five and up, add one is the game.
Now flex your muscles like a hero,
Digits to the right turn to zero.
All other digits stay the same,
Wow, you're a winner in the rounding game.
5. CUBA method
C- Circle the number you are rounding
U- Underline the number to the right
B- Baby or Bully? Baby (0-4) stays the same Bully (5-9) round up
A- Add zeros to all the places behind the circled number
Hope these ideas are helpful. Anyone have something else they use to teach rounding that you found helpful for your students?