Grades 3-4 Video Solutions 2012-2012_3-4

Video Transcription

Problem number 21. A special clock has three hands of different lengths. One for hours, one for minutes, and one for seconds.  We do not know which hand is which, but we know that the clock runs correctly. At 12.55 and 30 seconds p.m., the hands were in the position shown on the right.  What will this clock look like at 11.00 p.m.? Here is a close-up of the clock. Like on a normal clock, the longest hand is the minutes.  Because it is pointing at 11.00 and on a clock 11.00 is 55.00, this means that this must be the minute hand.  This hand is the hour hand. The time is almost 1 o'clock, and that is why it is pointing towards the 1.00.  And then, because there is only one hand left, that means this must be the seconds hand. And it is also pointing towards 6, which again is multiplied by 5, which is 30.  So, looking here, we see that the longest hand is the minutes, the second longest one is the hours, and the shortest one is the seconds.  And the time we are trying to find is 8.11 p.m. Let's start with the seconds hand.  This hand must be pointing directly at the 12.00 in order for there to be zero seconds on the clock. At 12.00. And now, we will move on to the minutes hand.  It is supposed to be 11.00, which means that it would be pointing around here, right next to the 2.00.  And then, the hours would be on 8.00, which means it would be right next to the 8.00, because we are already 11 minutes into this hour.  And if we look here at E, we see that the seconds hand is pointing at the 12.00,  the minutes hand is pointing right next to the 2.00, and the hours hand is pointing at the 8.00, which means our answer is E.

Video Summary

The problem involves determining the position of hands on a special clock with unknown hand types at a given time of 12.55 and 30 seconds p.m. The longest hand was identified as the minute hand, pointing at 11 (55 minutes), the second longest as the hour hand, pointing near 1, and the shortest as the second hand, pointing towards 6 (30 seconds). For 11.00 p.m., the second hand should point at 12, the minute hand near 2, and the hour hand near 8. The correct clock display corresponds to option E, with these positions aligned.