Elapsed Time (AM and PM)

Here the elapsed time is found for situations that cross from morning into afternoon. Across AM and PM (on a Clock) keeps one format throughout, covering hours, minutes, and hours and minutes together, and confirms that the hands keep moving straight through noon.

Taking 11 a.m. to 1 p.m. as ten hours, from the gap between 11 and 1, is the reliable error: the numbers on either side of noon are simply subtracted. The sign is an answer longer than the real interval, which shows that afternoon times are not being recounted from 12 noon.

Up through Elapsed Time, the movement of the clock hands stayed contained within one half of the day. Here it is confirmed for the first time that the hands move the same way even across noon, and this same situation, crossing from morning into afternoon, comes up again in Time and Duration in grade 2.