A teaching clock for teaching the concept of elapsed time includes a clock face having a minute hand and an hour hand pivotally mounted to the clock face and an elapsed time indicator having an hour hand and a minute hand that move synchronously with the movement of the clock hands. The hour hand is connected to the minute hand such that pivotal movement of the minute hand about the clock face causes the hour hand to pivot synchronously therewith to designate a progression of hours of the day. The minute hand and hour hand are selectively positionable to display a time of day. The elapsed time display may include a releasable connection connected to the minute hand such that the elapsed time display resets to an initial or zero position upon release of the releasable connection whereby an elapsed time is shown by the elapsed time display between any two selected times of day shown by the minute hand and hour hand on the clock face.

 
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> Mastery-based drill and practice algorithm

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