Home : 2003 : October : 21
rounding
By Colleen
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I used to draw a "mountain" (basically an inverted V) There was a story about an old lady (me) climbing the mountain and having to rest before going down the other side. I always rested at the halfway marker. The mountain| would be labeled (for example) with 20 at the base on the left, 30 at the base on the right and 25 right at the top. An "X" would be placed at the approximate location of the number being rounded. If it hadn't gotten to the top, it belonged (slid down) on the 20 side. If it made it to the top or part of the way down, it belonged on the 30 side. It seemed to work well with 3rd graders | |
and lower functioning upper graders. This can then be applied to a number line.
Round 52 to the nearest ten. What two tens numbers does 52 come between? (50 and 60)Draw a number line segment and label 50 and 60. What is halfway between 50 and 60 (the resting place)? (55) Place 55 halfway along the line. Where does 52 come? (after 50, before 55). Which ten is it closer to? (How many "steps from 52 to 50? How many from 52 to 60?)Also: "0 to 4 is no more; 5 to 9 move up the line" This seems to help them remember "which way to go." I do agree, though, that they need a lot of practice telling "which two tens numbers does 47 come between?" (The 4 that is there and the next one up)
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