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# Today in the Math Lab... Our open number line is constructed from colored electrical tape on a chalk/dry-erase board.

Today in the Math Lab we used the open number line to:

• approximate decimal placement with fourth grade,

• and approximate time with the minute hand with second grade.

To approximate decimal placement, a star magnet was placed on the number line and students had to estimate the whole number and nearest tenth that matched the placement. Students were then given a number, such as 4.3, and had to place the magnet where they thought the number would be represented on the number line. In both cases, students had to explain the rationale for their decision.

To read fractions on the number line, we drew lines down from the markings and created a strip diagram below the number line, shading the spaces to the marked point. This helped transfer the knowledge students already had about bar fractions to fractions on the number line.

To approximate time, the magnet was placed between 3 and 4. Students practiced saying, “some time after 3”, and “3 and some more.” We then took a number line strip, slit it along the upper edge, and made it into a circular clock face. A little hand pointing between 3 and 4 then indicated “some time after 3”, and “3 and some more.”