Arithmetic Grade Three

Lesson One hundred and thirteen: Rounding and Multiplying

Review of rules for rounding to nearest 100:
  1. If the number in the tens column is 4 or less, then round down. (Example: 544 -> 500.)
  2. If the number in the tens column is 5 or more, then round up. (Example: 550 -> 600.)
Special Case:

If you get a number like 650, it rounds up to 700. Also remember that if you are asked to round 300 off to the nearest 100, then you do nothing since 300 is already rounded off to the nearest 100!

Rounding to Nearest 100 and then Multiplying

Here's an example for you: 


      ORIGINAL    		ROUNDED
       PROBLEM			PROBLEM

        236	---->		   200
      x   3 	---->		 x   3
     -------		       --------
				   600
Although the answer to the rounded problem isn't the same as the actual answer to the original problem, it does give us an estimate. 

      ORIGINAL    		ROUNDED
       PROBLEM			PROBLEM

        455	---->		   500
       x  3 	---->		 x   3
     -------		       --------
				  1500

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